I tried, fellas.
But when loadiing DOS + handler, with the way that the extant R: handlers load, there isn't enough RAM to handle the 8K needed for the high resolution display + the additional bytes needed for various bits of scratch memory.
I'm sorry. while the PLATOTerm cart is 16K, it needs a bit more than 16K with DOS loaded.
(without DOS loaded, I was able to shove the memlo down far enough that it runs fine, but I can't dynamically do this without drastically rewriting the cartridge init code.)