Its a tricky question since it necessarily depends on how much work the devver puts into it...
ie: The Zodiac *does* have a 2d processor to do some cool stuff; so without it, its just another aggressive 200Mhz machine, so emulating an Amiga or GBA would be rough (the GBA being rougher, due to hardware scaling and rotation which the Amiga didn't even have).
It also depends on the Amiga support; ie: Does it handle some crazy Amiga stuff, or just the core simpler Amiga stuff?
Does the devver write any of it in assemble, or with the exact platform in mind, or a generic emu?
That said.. I doubt GBA is doable halfwya usefullly on GP32, since its a software only machine. Is it doable on the Zodiac? Well, its certainly much more possible than on the GP32, but it woudl require using the hardware to do a lot of the tricks, and the emu likely needs lots of work to support this.. ie: Existing GBA emus all do their own scaling and rotation in software, so the devver woudl have to make it use the hardware instead. Is the hardware generalized to do scaling from memory to memory, or only from memory to screen? I haven't looked that closely.. so can the Zodiac do GBA? I dunno. Not likely, but its in the realm of possibility if the hardware is used well.
Amiga? Should be an easy test;l most people use UAE for their Amiga fix, and writing a new Amiga emu for core Amiga fucntions is possible (like CaSTaway is for the ST), but a lot of work (mroe than CaSTaway). So assuming the dev audience is small, it woudl likely be a UAE port.
Anyone got a 200MHz PC around that can run UAE and see how it performs?
Thats the trial by fire
But we're certainly getting there; the Palm T|C and T|T3 both clock in at 400Mz, and I've overclocked my T|T3 to 678Mhz successfully (in software, just like the GP32).
400MHz is getting "there" to the sweet spot for emulation, and 678MHz is crazy ass.. shoudl be able to do mos things there.
So even if Amiga and GBA are out for now, their time is coming VERY soon. Maybe on the Zodiac, but it'll be awhile until we get some "devoted" people. (ie: Like me for the ST.. I never had an Amiga, so I doubt I have the energy to get that much into it
jeff