Aha, the second of those points out something I didn't know, which is the ability to store a 24-bit address in zero page and indirect through it. That relieves the memory addressing problems considerably, although it's going to be fairly slow.

I was working on the BotStik software for the Apple II and BBC Micro in 1984-86. When the Apple //c came along, we concluded it was a marvel of misplaced ingenuity, and continued with our MS-DOS product, which lasted into the 1990s.