these are interesting hacks, glad you let people know about this possibility.

It is a very nice keyboard layout. I'm very happy I discovered it (even if it was by mistake!)

Another example I can think about: remap the Ro key to toggle between international layout while it's pressed, so you can switch between layouts with a key right next to the shift key.

For example, on a US/RU settting, press Ro while pressing the 6 keys to the right of Tab in a sequence and you would get ЙЦУКЕН, don't press Ro and do the same: you would get QWERTY. Mixing and matching in both upper and lowercase would be very easy.

Could you make the key under the C act as a Cmd/Ctrl key like a Mac?

There are probably many ways of doing it at software level, I would suggest either of these two cross-platform tools:

[1] https://github.com/kmonad/kmonad

[2] https://github.com/jtroo/kanata

With the extra keys, you can have 4 modifiers on each side of the space bar: Control, Win (Super), Alt and Cmd - total 8 modifiers, ideal for your thumbs!

This still leaves you with the Yen and the Ro key to map for other things!