I would get this if the green pcb didn't stick out of the console. Is there a way to make it flush?
I agree with db on this one. You can do it, but it'd suck.
Some existing converters have you stick the HuCard's contacts into a connector, which then bends around and you've got all sorts of crazy vias (the things you see on circuit boards when signals go from one layer to the other) and crap everywhere to deal with. And even then, they aren't flush with the front of the console (they still stick out a bit, because the HuCard on top needs to have somewhere to go).
One thing you *could* do is, if you don't have a CD-ROM unit attached to the TG16 or PCE, all of the HuCard's signals exist on the back of the unit, so in theory you COULD put a second HuCard slot dedicated to the other console back there. But that would be kinda silly.
... The "no" you got from esteban is looking really good right now, but really, there are many ways to skin a cat.