I've recently heard that the memory control module is actually in the seats. And it should work for the seats.
But it won't work for the mirrors and steering column if you don't have the parts (memory mirror motors, and whatever the column needs and who knows what else).
I'd guess the 12 pin plug when fully wired is for the mirrors and the column as those would be controled by the memory control module in the seat.
Seeing no reason why the seats won't work as regular seats. and they should even work as memory seats. You just won't get the rest of the memory stuff that's usually in a factory memory seat setup.
Sorry, I've not yet pulled my memory seats to see what things look like underneath to give you any better answers.
Cosmos Black/Black 1995 540iA M-Sport
BMW Individual Exclusive Edition, 1 of 65 total, 9/25/95 Build