I really dislike the extremely harsh wrinkles that are in the default Adult skin, they really get in the way of recreating people that aren't necessarily young but that also aren't quite that weathered. Is there a default replacement out there that makes them more subtle, or even disappear entirely? I know SimsOnTheRope has a custom skin detail that makes them fade away, but I'd prefer a default solution (especially since alien sims can't access skin details). Thanks!

Warning : *I might say something completely retarded due to my lack of knowledge in this domain*

Could you just replace the Adult default skin by the YoungAdult one, for both gender, for a quick fix?
The age details are obviously ON the skin, since without adding any skin details, aging a sim from YA to A adds aging details.
You would then have no difference between both ages, and could then decide to add some (face details) or not.

I tried to do that, actually - there are semi-transparent areas on the skins around where the mouth creases are, and even though I managed to make the eyebags more subtle without much difficulty, I can't get rid of the mouth creases without messing up the way the faces are composited. I don't much like the overly convoluted system they chose to go with for skins in TS4, it's a bugger to work with.

Ok. but does the YA skin has those too? I am not sure I understand now. lol
Is the YA skin and A skin are different texture files? because if they are..I would just copy YA to A. I would not try to edit A..

They're different files, but both of them are transparent in the area where the mouth creases are, so copying the YA skin over doesn't actually change anything in that area. I'd have to do some fairly serious graphic editing to fade the creases, and I'd rather download someone else's version if it's already been done.

Oh ok, I see.