...and I really would like to know what options I still have available to me in terms of systems.
I tried Mudlet and we didn't agree on a lot of things, so really at this point, MUSH is my only option. But as far as I can tell, development of systems and plugins for MUSH seems pretty much dead.
Is there anyone out there still using MUSH with something homebrewed, or perhaps you kept it updated with all the changes going on. If so, please let me know! I'll pay you if you share!