Each interface EnterMice can use the adapter SEGA.
Okay, it is cool, I misunderstood this yesterday, because of this:
This is your set.
My bad, sorry for the missunderstanding.
But (how you can see from the post of Jolaes76, too) if there would be games using multibutton controllers (and the sega is probably the widest available multibutton thingy),
those who have entermice (probably) would like to give it a try ...
So EP lives in the emulator mostly ... but there are some active real-steal EPs in the wild, some hundred maybe, nobody knows,
and some of their owners are interested in hw gadgets and expansions, and they use things like your EnterMice, SzörG's SD cartridge or Saint's internal memory stuff.
So it is a very limited number of EPs, but If somebody already GOT an EnterMice instance, (I think only) probably they will get a sega conroller ASAP,
when (or if) a sega controller using game will be available ...
So, if you could make it possible the ordering the sega extension for the EnterMice, that would be the clean solution, because most of the people cannot even assembly that, and for those who can do it, it is simply easier to order one than assembling.
ONLY IF you would bother with this, maybe you could ask first the forum here, who would like to get that for the price you could bother with that.
And in that case I'm wrong, and only a few of the EnterMice owners will be interested in the sega converter, you can drop the bothering with it, still.
But, of course, if the sega converter is out of the scope of the "official" EnterMice and remains an optional extension of the EnterMice assembled by the EnterMice's owners,
that will not be the end of the world, still ...