While I'm usually quite prone to compromise, in this case I think a community-driven Firefox OS should have a somewhat extreme design. Given that resources would be far less than they have been (and were not enough anyway), no compromise is possible: either something is essential, or it should be dropped. This is the case, I think, with the Marketplace: it's resource-hungry, has been quite disappointing so far, and, most of all, it is not "web-like". Apps are just one of the paths an OS can follow, and I think FxOS should look to other paradigms.
The good news is, Forefox OS would radically shift its market target: not anymore first-time smartphone users, but tech-savy people (where tech-savy means being able to follow the guide to flash FxOS on a device, nothing too extreme). This means a lot of old concerns can be dropped: to hell the Marketplace, we don't need that, we know how to find content on the Net already!
This though brings forth another issue (or better, THE issue): who's making choices? Let's say we have to choose whether to keep or trash the Marketplace, and we have different but sensible opinions on the matter. Mozilla's lead meant that there was someone in charge with sufficient knowledge, experience and influence who, after listening to the userbase opinions, made the decision. (Or it should have, I don't want to discuss Mozilla's choices here.)
The issue, I think, is that an OS is a HUGE project to manage. It's not possible to just make a list of proposed features and vote for them, the project should follow an organic vision, which at times may go agains't the userbase's direct wishes (for example by dropping the Marketplace, which would surely anger many users and app developers). I don't know who may have sufficient knowledge, experience and influence (and interest in FxOS) to lead such a project.
Reguarding FxOS missing features, I'm not talking about essential features: I'm using a FxOS device too and I can do mostly anything with it. Though, this doesn't mean there is nothing left to do. Quite the converse, I think, to be somewhat comparable with other mainstream OSs. Just to name a few:
- Push messages/notifications everywhere (at the moment the Email app checks every once in a while).
- Sync everything (history, passwords, contacts, bookmarks…)
- Full disk encryption
- Homescreen (now it's so bare-bone)
- Voice assistant (every major OS has one already)
- Transition to NGA is frozen halfway I think (but I may be wrong)
This is just to list a few, but there are also more general issues: performances (now the comparison with Android, on the same hardware, is not so good) and tons of small features and fixes (and small features and fixes make the difference, just think how polished Android and iOS are).
I wrote far too much. This won't be an easy task and I'm quite pessimist about it, that's what I wanted to express. Still, I'm happy so many people care for and belive in FxOS!