OutcaST is one of my favorite emulators, it runs lots of ST games full speed.
Still there is room for improvement:
- sound
- command line support (for gpmenu2x)
- STE (you can use the STE rom for STE enhanced games)
- compatibility (lots of homebrew will not run, but also commercial games fa Jumping Jackson)
- better save state handling and user interface in general
You are right, there are not too much games developed for STE, but there are a couple nice ones (fa Obsession)
Skeezix is on a well deserved homebrew journey (and a nice one I might say), so it could be time for another dev to step into the ST arena. According to the Hatari site it should be possible to run Hatari on a 200Mhz machine.
It's not up to me to decide if it is woth a devs time, but I like the ST. It looks like Amiga emulation will never be as good as the ST on the gp2x, so why not improve ST emulation.