I understand your dilemma. Right now Steward and the community are in excitement with the rs-97. Steward is implementing "what's possible" on the device right now. From the release notes, a lot is going on. I think it's great and fun.
Personally, I would prefer the approach to start small and get bigger. As in, make nes, sms, gb(c), snes, and genesis all stable emulators running optimally. And continue to add to that list as an emulator has become stable. After emulators, work on gui, backgrounds, themes, apps, and visual goodness.
It seems the approach now is to go huge and hopefully in future releases back down to things that are running 95-100% and optimal.
That being said, if you can't work with the stuff Steward is doing... You're spinning your wheels at this point. Maybe in the future that will change.
I definitely think that you should continue to work on what you've done with the stock firmware at this point. Or play around with anything that could make the existing emulators you have put together for the kiii plus to run better. Check out the Pocketsnes that @blackz1982
mentioned. And someone mentioned Dingux-2600, Stella and Dingux-7800 as running well. So you could check those out and see if you could do anything with them. Keeping the best of the best on your dmenu project is something I would look highly upon.
I just found the backup file that you linked. So I will try out your dmenu and emulators. But from the sounds of it, your work is more on par to what I like (more optimal performance emulators). In not so many words, less is more.
Keep up the good work! And keep pushing forward!