I'm somewhat involved in the dev side. Check out #htc-linux on freenode for dev chatter. I don't think you'd get much out of a custom WinMo ROM... most of the device exploration is done with HaRET and the haretconsole (good docs
here, but a lot of the functions are not clear to me, being far from an engineer).
That and adding tons of debug info to the linux drivers are the tools we have to track down where the problems are. It's not the most efficient method, but we're stumbling towards more functionality.
There's always room for more people looking at code and helping out. I can point you in some of the right directions, but can't do much as regards GPS or camera, specifically.