I would love to spearhead a mod project of creating 3D interiors for many buildings. It would be truly awesome even if you copy pasted a lot like the apartments in online. Just being able to go into all those buildings along Santa Monica and Venice Beach.
I believe we've hit a peak in what visuals we get in a GTA game but the next area of improvement will be bringing the world to life and hopefully a bump in scale again. You go back to San Andreas and look at the Vinewood sign and then compare it to the one in V. That's the best example of the scale jump we got from the 3D Era to the HD Era I can think of. Imagine what the next jump would be.
Do you know much on modelling and stuff? I've been thinking of some stuff for some interiors for that Willie's supermarket and I know pretty simple modelling. If folks can work together and make it into some crazy cool Walmart-esque place, it'd be pretty cool.