You're missing the original point.
I use a PS2 keyboard quite nicely on my Minimig v1.1 (the minimig is actually in the keyboard).
What we're looking at is reusing old A1200 shells that are left over from tower conversions or have dead mobos and giving them a new lease of life as cases for this new Minimig.
Throwing on of these Minimigs into an A1200 case and then snaking a PS2 keyboard out of the side will look a but "funky". Bastardising the A1200 keyboard to put in a PS2 keyboard seems criminal (but might be the only option). If I go that route then I'll use a black PS2 keyboard and spray the A1200 plastic casing black to match.
The A1200's keyboard interface is not a difficult thing to adapt to the Minimig. If there were a decent market, could make custom minimig boards. If not, can do an A1200 to PS/2 adaptor. Either way, piece of cake electronically. Anyone with 15 minutes could whip up the schematics needed based on the numberous PS2 to Amiga adaptor schematics from Aminet.