I'm a programmer (not a pro-gamer) working on a new tool which will drastically expand the capabilities of UMS maps as well as make authoring way easier (no more trigger bullshit). It doesn't use EUD, doesn't require client mods and can't be patched out. The tool is quickly becoming usable and I need someone to help me with testing and feedback. Let me know in this thread if you're interested to help. Experience with SCMDraft 2 and/ or the Blizzard editor as well as (really) basic programming skills are required.
EDIT: Initial version has been released. Check out this post for info - http://www.teamliquid.net/forum/brood-war/521681-custom-map-ums-creators-wanted#19