Well, that is a full-featured, complete (more or less) mission right there, not just a testing sandbox.
You could play it right now. It's just not quite as awesome as we want it to be. (Though all the major capship control problems of the past have been solved.)
You know, at the very least, you could do the community a favor by post the bare-bones bits of the mission with all the names ripped out or the like, just the scripting necessary for correct control.
We are absolutely planning to do that. We've already posted most of our custom scripts for effects like beam piercing and debris fire. I'd be happy to put the FRED-side stuff up as well, once we're sure it's all done.
The FRED-side tactical menus should be totally modular. The scripts, however...well a number of them work very specifically for
this mission, using only a Karuna; it would be easy but not totally non-trivial to adapt them to other missions (i.e. we could do internally in five minutes, but the average end-user couldn't) and also easy but even less trivial to adapt them to other ships. They could be adapted, but probably only by somebody with scripting expertise.
...when that stuff hits the regular releases.
All the scripting in this mission can be done on existing builds, I believe. The one feature that couldn't be done now is the removal of the red damage flash on big ships, which for the moment is BP custom.