Using an atmega kind of kills the fun, it is many times more powerful than the z80 "cpu"
Worth noting that 16V8 and 22V10 GALs are still being made too, and I’d argue that programmers for them aren’t exactly “outdated”.
Not that I have anything against this design, I’m always happy to see a new SBC, though it could be argued that it still “hides” more of the bus inside the MCU than would perhaps be ideal.
are cplds okay
you can get currently-manufactured cplds for under two bucks
https://www.digikey.com/en/products/filter/cplds-complex-pro...
and probably nobody is going to say that an lc4032ze or an atf1502 is faster than a z80 (i mean, it's literally faster, in the same way that a 74hc04 is, but you sure aren't going to emulate a z80 on it)
Especially for the Atmel 15xx parts, the software is windows-only, old and annoyingly crash-prone. The GALs are at least programmable from modern OSes with commodity programmers.
That said, the CPLDs themselves are good chips, and I don’t think especially inappropriate for a vintage project
The original owner of the item makes numerous small changes and repairs over decades which preserve and improve the functionality.
They finally sell it off to a collector who reverts all the changes, degrading the functionality in order to restore some notion of authenticity. And sometimes they go further, fixing “mistakes” made by the factory.
In this case, the functionality of a Z80 is so ridiculously outdated and obsolete that I suppose authenticity (and nostalgia) is really the only point.