I'd probably end up translating the MSX or PC-88 versions. Though it appears Denzeni Land and possibly the other games were only released on the super ancient cassette tape format. I think if I were to attempt to translate them, I'd be the first person to hack a cassette game to my knowledge. I could be wrong on this, but I believe all the data on a cassette basically gets loaded into RAM at startup and is basically a ROM.
At the very least though, I'm gonna wait until I find an auction for the games at a cheap price and try to buy them, have them sent to me and then send them off to be dumped. I suspect it'll be a while before I get to the point of starting a project for these games.
I've released an update that addresses the random freezing in the second half of the game. It hasn't been tested extensively but as far as I can tell, the game should be more stable now.