Oh, but I appreciate all feedback

First of all, I should prolly apologize for not updating this quite as frequently as I "almost promised". Secondly, I totally see what you mean with everyone having ideas all the time. Coming up with games has been something I've done for as long as I can remember, and in my younger days, they were indeed mostly GTA in space or Mario Bros with different looking enemies etc etc.
I personally think I might have something good going here (who doesn't love their own ideas?), but naturally it'll be impossible for ya'll to see what makes it so glorious because... well, all of those reasons you mentioned. So here's a few "out-fleshings" from the draft I saved a while back;

- Planet resembling earth -
With this I mean in terms of climate, cities, culture and wildlife, rather than landmass. While some alien elements may be added (hence "resembling"), the player should be able to know what to expect from the environments. Not only to make it easier on newer players, but also to allow more experienced ones to utilize strategies inspired by real events.

- Light sci-fi -
Mostly realistic technology with some things altered or added to improve gameplay. I'm talking bigger guns, faster cars and cybernetic implants, rather than doomsday-lasers and demonic robot soldiers.

- Civil war -
This allows for many different factions, of which most would be formed by players. No faction would gain from just steamrolling the civilians, as their loyalty and support is the ultimate goal. Basically, there'd be two ways to capture cities/areas. Either by military supremacy, or by gaining the local populations favor, making it extremely hard for rival factions to operate there.

- Mostly urban areas -
Huge megacities or tiny villages. Claustrophobic industrial complexes or cozy bars. Urban areas offer great diversity, and lots of people to inspire/opress. As with most MMOs (and real cities, of course), there would be bars, shops and other hotspots. I'd aim to have as much as possible available to players, including their own shops etc, but these would have to be very different from the respective NPC versions.

As for the whole deal on the characters, by heavy class customization I mean something leaning more towards EVE Online's skill system where you start with a set of skill but are free to train in whatever direction you want as the character progresses, perhaps without any predetermined classes at all. Different types of equipment should allow you to switch between combat-roles, rather than determining who's got the best character. For this reason, I'm thinking players could customize their own equipment kits to bring with them to combat, or whatever they need them for.

Example kits:

Main item: Machinegun
Secondary item: Kevlar armour
Support item: Implant increasing runspeed

Main item: Pistol
Secondary item: Super-comfy trousers
Support item: A healthy snack

The machinegun-kit will obviously be more effective during an intense battle for a city hall, but the guy with the pistol will have an easier time flanking or perhaps providing the machinegunners with ammunition and updated maps. In a game such as World of Warcraft, however, the machinegunner will almost certainly win, because there isn't much more to it than having the most spikes on your armour and/or the most particle-effects on your weapon.

(no preview button, so this post might very well look completely forked)