I am warning you, I have zero experience in TS4 modding.
But I am curious, and I'd like to know if completely replacing the TV channels is somewhat possible to do.
In TS4, all TV channels features TS3. If I wanted to replace what's on TV with TS3 channels..which features TS2...could this be done?
Some channels might not be present in one game or another, but maybe I would simply not edit/replace these ones, or these channels could show *snow*..interference.
One could pretend that Not every Sim has cable TV! For instance.

Do you mean the channel names, or the actual pretty pictures as well?

The pretty pictures, yes.

I'm pretty sure it can be done, but it'd be a rough journey, to say the least.

If you use Sims 4 Studio and go to the Game File Cruiser, you can see AVI is one of the file types in the database.

What you'd have to do is make your own little avi, and add it to your own .package file with the same group and instance IDs of the one you were replacing. Anything that has the same ID as an existing resource overrides that resource in the Mods folder.

The trick is that you'd have to know which AVI does what, and that's going to be a trial and error process. Extract from the database, play it in a player to see what it is, document it, rinse and repeat.

That seems easy enough..long maybe, but easy.
But I would not make my own little avi though, I'd take the ones in TS3...and this is where it might become complicated, if not totally impossible. I have no idea if TS3 TV use avi as well, and if TS3 avi can replace the TS4 avi ? Are they even compatible, recognized etc.

It's very easy to extract TS3 video files out and put it into the TS4 because they use the same codec's so re coding them isn't necessary, but because they are different sizes you get bar bars on a 16:9 TV but good news they fit perfectly on a 4:3 TV, unlike the black bars TS4 gives on those screens.

Follow this tutorial, its not really hard as it looks, and more you do it, the easier it becomes, before you know it, you will find your own quicker way of doing it even without referring to the tutorial.

Link

It's possible to play video stream instead of avi...
Currently I am working on youtube player for ts4.
But I have no plans to publish that mod...
Possible, I'll done it and it will be left unpublished, as many of my projects...