What could these developers bring to Nintendo?
Vigil Games
Radical Entertainment
Raven Software
Volition Software
P.S.
Not the IPs they have already worked on recently.
Sorry to hijak the thread with my silly essay, Kytim.
For fun and to get an idea of their strengths, lets look at what these studios have created. I will just pull out some notables according to my eye:
http://youtu.be/IS7Og1zvdy8Raven Software
Developed: Hexen, Heretic, X-men Legends, Marvel Ultimate Alliance
Shoehorned-in Nintendo property I could see working: Nintendo RPG (cross btwn Mario RPG and Ultimate Alliance)
BTW: they already belong to Activision
Radical Entertainment
Developed: Battle of Olympus, Mario's Time Machine(!), Simpson's Road Rage, Tetris Worlds, Hulk Ultimate Destruction, Scarface, CSi games, Crash Bandicoot licensed games, Prototype
Shoehorned-in Nintendo property I could see working: Star Tropics!! ...uh, Mario Battle Kart!!...dunno, these guys are all over the place
BTW: they are on the sales block and may be closed down by Activision, most employees already released
Vigil games:
Developed: Darksiders
Shoehorned-in Nintendo property I could see working: Eternal Darkness or action-oriented Zelda spin-off (assuming Ninty owns the rights)
BTW: owned by THQ, maybe their best studio
Volition, Inc.:
Developed: Freespace, Descent, Red Faction, Saint's Row
Shoehorned-in Nintendo property I could see working: mature Balloon Fight, mature Tingle's Rose-Coloured Rupeeland
BTW: owned by THQ, maybe their best studio

One question though, Kytim: I know wishful thinking is one thing, but why do you assume Nintendo could just acquire one of these studios for a reasonable price? Radical Entertainment perhaps as they are actually on (fire)sale, but they have little prior history with the Big N and are under some...administrative...distress right now. Nor do any of the other studios on that list.
Any purchase of an established developer would probably require a collaborative history and positive relationship. As others have noted, a Monster games or perhaps Kuju Entertainment makes more sense. Or Sega* (my own wishful thinking) just to get their hands on IP like Panzer Dragoon and Virtual On

*just checked their valuation again and Sega would be, as expected, too expensive. It would be more like a merger given the relative sizes ...and the history of successful mergers is spotty at best