Custom vacation destination: when adding a vacation destination, instead of Takemizu Village, Three Lakes, Twikkii Island or Add all, click on one of the three pictograms beneath, the pagoda (Far East), the island (Tropical) or the mountain (Mountain), to pick a map (sc4Terrain) for your new subhood. This choice determines what special gesture and dance the locals will perform and which special sim (Witch Doctor, Wise Old Man or Bigfoot) will inhabit the hidden lot.

Custom hotels:
Build community lots to your liking, maybe some residential lots to buy too, and build hotels.
I like to build some free staying place where sims will sleep in tents (like Three Lakes' Axe Wood Campgrounds) for my students and nature lovers. If you do that, you don't need the hotel podium, the tent will be enough to "check in".
To build a hotel, start on a community lot. Build to your liking, not forgetting:
to add a hotel podium for checking in and out
to use the appropriate hotel doors in the rooms. Like in real hotels, the room number is outside, the safety map is on the inside.
like in dorms and apartments units, make sure the rooms have only one entrance/exit
don't put decorating objects such as paintings inside the rooms, as these will appreciate over time, and the room price will increase consequently.
Save. Enter the cheat code changelotzoning hotel , save again and exit.

Custom hidden lots:
Back up your neighbourhood now if you haven't already done it.
Maybe build your hidden lot, at least the tropical and mountain ones, in a dummy hood to make sure Bigfoot and the Witch Doctor really do show up when you visit, then if they do, place your lots in the real subhood or copy them if they are beach lots.

Far East: only the Tea Time Table, found under Surfaces/Misc
Tropical: the microwave, the cheap dishwasher and the Feel the Breeze Hammock (the one between palm trees, it won't work with the simple hammock). As a general rule, stay as close as possible to the original hidden lots if you don't want to have to edit them again and again. I usually give the Doctor a small kitchen and bathroom, but no TV. Beach lots work (I haven't tested this for the other destinations).
Mountain: this one is the trickiest, as it requires a residential mailbox and, apparently, to be built on a medium size lot only (screencap of the BBS in the spoiler, as the BBS no longer exists) The other two can be built on small lots (tested) or big ones (like the original hidden lots). Bigfoot also needs the cheap stereo, I put it on a coffee table, that's where it is in the original lot, and I haven't tested without the small hammock but maybe the stereo is enough. As usual, build and decorate to your liking, toilets(!) or a small fishing pond come to mind, but don't go crazy, I think that if the lot is too "heavy", Bigfoot won't show up: I've had him not appear, then appear after I had deleted some of the trees (I wanted his burrow to be really hidden in the woods and stuffed the lot full with trees).

As a general rule for the hidden lots, maybe stick to no-CC objects and deco, because having to edit the lot afterwards because you deleted a wallpaper will require to use SimPE again and go through all the loading screens again and again.

Edit.: actually, you can edit Hidden Vacation Lots without using SimPE.
-Load the vacation sub-neighbourhood whose Hidden Lot you want to modify
-The Hidden lot is invisible, but you can still load it in build mode thanks to the LoadLot cheat.
-Make your changes.
-Now, the "save" icon is greyed out, you cannot save your changes. To be able to do it, you need to change the Lot Zoning.
Enter the cheat ChangeLotZoning community, now you can save your modified Hidden Lot. When you're done modifying the lot and saving, type the cheat changelotzoning secretvacationlot
-You cannot save anymore, just exit the lot. Your modifications have been saved and will be visible the next time your sims visit the Hidden Lot.

Now, how to build custom hidden vacation lots:
as mentioned, for Bigfoot's cabin, start on a residential lot. Build now or you can do it later. Enter the cheat code moveobjects on , and move the mailbox and trash can somewhere else on the lot. Enter the cheat code moveobjects off .

Save. Enter cheat code changelotzoning community and save and exit.
Re-enter the lot, buy a public phone (Electronics/Misc) and a public trash can (Misc/All, 75§ or use the community tab: ) and put them somewhere on the lot. Save.

The building of the Far East and Tropical hidden lots starts here, as they don't require a residential mailbox. Build and decorate to your liking. When you're done, save and EXIT the lot.
Re-enter the lot, enter the cheat code changelotzoning secretvacationlot . You can't save anymore, exit the lot.

I suggest marking the neighbourhood somehow (I put trees all around my hidden lot), to know where the lot is once you make it invisible, and avoid placing another lot "on top" of the invisible lot, in case it's a bad thing.
Once upon a time, to hide lots, it was enough to bin them, then place them back in the neighbourhood. But some EP broke that, and now, if you bin a lot after changing its zoning to secret-whatever, it will vanish from the bin and only be visible in uni subhoods.
Today, lots are made invisible thanks to SimPE and a little trick argon discovered.
Exit the game, launch SimPE, Tools/Neighborhood/Neighborhood Browser... and select the main neighbourhood on the left, and the subhood on the right (scroll down menu), and Open.
In the resource tree (top left), click Lot Description (LTXT), find your hidden lot by its name, click it.
In plugin view, in the lower part of the window, to the right of the lot picture, find UO: this is where you hide/unhide lots. To hide a lot, add 10 to the UO value; to unhide it, substract 10.
My newly built hidden Bigfoot cabin had a 0x00004021 value, I changed it to 0x00004031 to hide the lot.
Commit and save, that's it! Time to test your hidden lot.



What you will need:
argon's townie brick
twojeff's Sim Blender
Cyjon's NPC Maker Fix
Cyjon's Fewer Tourists

Custom locals:
For this, you will need the townie brick and the Sim Blender.
Time to populate those custom vacation destinations. You can CAS-create locals that will fit your ethnic/fashion criteria for "natives" of your custom vacation destination.
I suggest removing other vacation related hacks/mods, and definitely removing argon's make-vlocal. It was probably included in the townie brick, it's outdated and it's not needed. Cyjon's two mods and Pescado's antivacationactions don't need to be removed.
Create a family of several sims and add them to an existing family (to avoid leaving ghost family data if you are going to townify all of them into locals/tourists). Pause the game as soon as you enter the lot, and you can always remove the relationship with any sim using the Sim Blender.
With the future local selected, click the townie brick (buyable under misc/misc) and Make me...local/Mountains local/Tropics or local/Asia. The sim disappears from the family tree. Without unpausing, repeat for all your locals then vanish them from the lot using the Sim Blender (Teleport/Clear off...). You don't need the townie brick anymore.
You're done, you will meet those sims when you visit their subhood and learn special gestures and dances from them.

Custom tourists:
The once elusive custom tourists are now easy to create, thanks to Cyjon. You can CAS create them, or even turn existing townies into tourists, who will correctly show up in your vacation destinations and claim the other hotel rooms after your sim has checked in.
With Fewer Tourists and NPC Maker Fix in your Downloads, summon the townies you want to "touristify" or use your CAS sims. If the future tourists are members of the family (CAS sims you created and added), turn them into townies first using the Sim Blender ("Make Me a Townie").
At this point, the game is paused, and the future tourists are present on the lot, but not in the family tree on the left.
In debug mode, (= with boolprop testingcheatsenabled true), spawn the NPC and Townie Maker (shift+click on a sim/spawn...). It looks like the repo man's colourful gun. Shift+click on your first tourist to be and "Make selectable".
With that sim selected, click on the gun and "Make Me Into Vacation Sim.../Tourist 1". You need to briefly unpause the game until a pop-up appears in the top right corner ("Added to Family").
Shift+click on your new tourist and "Make Unselectable", then vanish him/her from the lot.
Repeat with the second townie. You can add him/her to the "Tourist 1" family (it will be named after the first sim added to that family, much like all Garden Club members belong to the Zarubin family in the original neighbourhoods). This way, they will be a family and share a hotel room together. You can make a couple, or parents and children, or anything, just don't make a family of a single child or teen ( or several children/teens with no adult/elder).
Alternatively, make your second tourist a "Tourist2", another one "Tourist3", and so on. When you're done, don't forget to make them unselectable, then clear them off the lot, and you're done!


Credits and sources

Please let me know if I've made mistakes!
There is a picture limitation in the forum's rules, so sorry it's very verbose and not very graphical.