Making an update with lots of clothes and customization would be great - it would be something different from the same old tired updates we've been getting.
Great, sure...realistic? Not at all.
Look at every game that has the level of character customization people in this thread and the entire forums seem to want for their specific areas. Do you honestly expect R* to give you Sims-level editing, NFS/Forza driving, premium 128-tick servers, Gary's Mod level of sandboxing...all for free? pretty much 3-4 AAA titles' worth of features of free via updates.
Yeah, not happening. This is a jack-of-all-trades. Not a master of them.
APB has a level of customization most people here seem to want... that game is riddled with microtransactions for every bit of clothing. It's either that or a subscription model. These wishlists would never be made for free. Not to the extent people want. That's my gripe with these "We want ___" threads; they tend to be unrealistic in practice.
E: Ha! Knew OP would mention APB. IF you expect R* to make for free what RTW charges for...good luck with that.
Also, You do realize that UE3 and RAGE are completely different in terms of allowing in-game model-morphing? There's a reason we no RAGE gta has the ability to modify your body type.