Like many projects - but especially open source project I think that nexuiz limits its potential success through one key factor:
Integration of the community.
I know you disagree, just stay with me if you can

I don't know much about software. I'm a long term linux user, and my only field of expertise is audio work - I'm a sound engineer.
I see a recurrent theme with pretty much all OSS sound software and I see the same thing with nexuiz.
- Professionals in a field are usually not good with understanding the workings behind the tools that they use. They just know what they like. Same goes for players.
- Developers do not like working with people who do not understand software, but I think they should anyway.
There are two Digital Audio Workstation projects that I think demonstrate this extremely well. Ardour and Reaper. Ardour is much older than reaper. Has a very talented base of developers, is open source, is very stable, has all the functionality you need but is unusable in a professional environment because its paradigms hurt the workflow for all common tasks so much that it's by a ridiculous factor slower than DAW's of equal or less ability. What lead to this in my opinion is a pretty hostile attitude towards the end user. It was a long and tedious process to even get into the mailing list, and once you're mainly getting ignored anyway.
Reaper started out very minimalistic with a small group of developers and had a precompiled (not svn) version with installer ready for testing that was updated almost daily during alpha/beta phase.
They spread the word through all recording forums, and quickly had a base of thousands of testers. The core of the project became the forum. The developers I felt took themselves out of the equation for the most part. If a request was approved by a good part of users, and it was doable, it was immediately integrated in the next version, where it either got thumbs-up or down by the rest of the testers (tester=anyone).
I changed from Cubase SX2 (€400 program at the time) to reaper (unexpiring shareware) during its beta phase and never looked back.
They did it by giving up their preconceptions of what they want it to be like, and let the end user decide. The result is the IMO fastest and most versatile DAW that is out there right now.
I think this pretty much translates to nexuiz.
What I think you should do is reach out to the players, and ask them to comment, and if they do: LISTEN.
I know that this is happening - it's happening with pretty much every software project, but I don't think it's happening nearly enough.