An emulator for Tandy/PCjr could work, by the grace of their framebuffers being in main memory.
Plantronics uses the same B800h segment as CGA, but puts a second framebuffer with another 2 bits behind it, at BC00h.
A problem would be if games used that range. I don't think PCjr would even have memory in that range. Not sure about Tandy. If Tandy is also compatible with regular CGA, it would have memory located there. And perhaps developers would then use that memory for both modes, to make things more consistent.
If they didn't, then you can do something similar to SIMCGA: Set up a timer interrupt and convert the Tandy/PCjr framebuffer to a Plantronics framebuffer periodically.
You'd still need to figure out where the framebuffer is actually located, but worst case you could just specify the value manually for each game.
I don't think there's a way to make it work for EGA, because firstly, you'd need memory at A000h, which is just above the 640k conventional memory. There are ISA cards available for that, but still.
Secondly, EGA has an onboard ALU, which determines how it reads and writes memory. Since we can't emulate that part, we also can't make sure the right pixel data arrives in the right place.
Since Plantronics uses a pixelformat that is neither compatible with Tandy/PCjr nor with EGA, it is not going to be very fast.
You need to reorder 32k of data for each frame, at the bit level.