I think this one will be pretty easy for you... Could you add support for DSSI effects? As far as I know, it should be a pretty trivial thing to do, as you already have support for DSSI instruments.
The reason I'm requesting it is because my project's suite of DSSI plugins (search for "LibModSynth" here on Sourceforge), currently contains 5 DSSI effects that can't be used in Muse2. Currently Qtractor, Rosegarden and jack-dssi-host are the only hosts I know of that support DSSI effects. I'm also working on a super-easy visual DSSI plugin designer, so I'd be willling to wager that there will be many more DSSI effects in the future.