In addition to my previous post...
Testing team
It might make sense to establish a "closed group" (informed and reliable) of testers, i.e. dedicated members of the community, who are willing to help the devs to test certain things ingame. Most likely these people will rather have to actually work than having fun wielding the glowstick.
If you get enought people together, you would always have a team to rely on. Testing could be more focussed, ordered and managed. Of course, this also means that testing with this team has to be organized.
Involving the Community in Development
I know that this on is a bit tricky in terms of style, quality and reusability of code. Everyone, who has ever developed software in a larger team knows what I'm talking about.
I bet, some members of the community would even like to help you out coding. You could post requests for functions (give a function prototype and post necessary info like struct and object defs), stored procedures, scripts, etc. (even libraries), which fulfill defined tasks.
You wouldn't have to go open source, but still benefit from motivated community members. However, you'd have to define some coding standards first, otherwise this would most likely result in chaos.