Wellllll.. No one has been interested because the community that actually uses either engine is dwindling. People aren't really playing mugen as much as they are creating things, or well just gossiping on the forums. In my opinion it is better than mugen in every way. I've managed to find workarounds to almost every issue that once plagued it. I advise you check out my channel. Every video is made using ikemen(besides the obvious cvs3 stuff). The modes of course are obvious differences, but everything else works the way it should. The only real issue is that ikemen doesn't read states above a certain value(custom) & I've worked around it by simply lowering it, or using another preexisting state that closely resembles it. Some of which you've said though is in fact possible. I've gotten lifebars to be fully functional. I have the guard system, dizzy, elemental codes everything working 100%. Myself & TheFclass97 have more recently discovered the issue with tag systems & eliminated the use of debug keys. We are this board lol. The two of us. We are the only ones whom have been working to improve it/experiment with it. If you check out his video you can see he has taken greater strides than I even have. He created a main menu screen, a character select, a stage select, a custom loading screen with tips & tricks, etc. Dude gets no credit. A big big step. Spoiler, click to toggle visibilty
VIDEO
Options Menu & Extra modesSpoiler, click to toggle visibilty
VIDEO
ChannelSpoiler, click to toggle visibilty
I've even used various types of characters & have had no issues whatsoever besides the custom states & occasional dampener not working, but manual fixes are the way to go. CVSSpoiler, click to toggle visibilty
VIDEO
KOFSpoiler, click to toggle visibilty
VIDEO
Capcom Vs.StyleSpoiler, click to toggle visibilty
VIDEO
I've done all this to "try" & help motivate the community into actually using the engine "LOL" as well as show them that each of these works. So in short more so than it is a problem with mugen, or ikemen itself its more of an interest in even playing. If I had to guesstimate.. About 35% of users on this forum actively play mugen.