I think in a unified platform structure (NX) they should be able to manage 12-15 full-blown retail titles every year no problem.
You actually don't want too many Nintendo games because then they start to cannibalize each other in sales.
I'd say increase Retro so that they can comfortably work on 2 games at once, and open another 200 developer Western studio.
Again if you combined their 3DS + Wii U output for the year you'd get a library that looks something like this:
Zelda: Majora's Mask 3D
Codename: S.T.E.A.M.
Fire Emblem Fates
Animal Crossing (lets just mix HHD and Amiibo Party)
Zelda Triforce Heroes
Xenoblade X
Splatoon
Mario Maker
Yoshi's Wooly World
Mario Tennis Ultra Smash
Star Fox Zero
Devil's Third
That's two Zelda games, a large scale RPG, new installements in several Nintendo franchises, a new major Nintendo spin-off (Mario Maker), and three new IPs (Splatoon, DT, and Codename: STEAM).
I'm even excluding things that might be redundant in such a lineup like the Xenoblade port for N3DS (though that would mean Monster could've made a different game) and leaving out games like Fatal Frame that shipped the year before in EU/Japan.
But that's a lot of Nintendo games to be honest. If you have more than that you're probably getting into the realm of overkill.
