Keep the 4.0 stuff in 4.0.
I say this because the 3.42 version has a massive enough textures as-is, and adding anything new to 3.42 always carries the risk that it'll cause some sort of one-in-a-thousand bug in said version.
I'll admit that I'm not a part of the modders battalion, so maybe this issue is a non-existant one, and if so, can be ignored, and if that's the case, then I can provide no further reasons why 4.0 stuff shouldn't be in 3.42.
As for the subject of raising the development time, let me just say that I'd prefer it if the modders battalion took as long as they bloody well please making this mod, and any others. Too many mainstream games these days catch it because of too-short development times imposed by corporate interests, and as such a mod like PoP, which has no corporate interests, should be fre to set its own schedule.