Wouldn't the recoup be substancially more damaging to Nintendo than the profit they already make?
You're assuming expensive R&D doesn't pay off when compared to be a merely publisher, but you can't back this claim with nothing substancial. If anything, R&D on handhelds prove to be a very lucrative bussiness for Nintendo.
Then we have the 30% increase ratio in profit-per-sale software, on which you could argue a Mario game definitively would sell 30% more in other platforms. But what about things like Pikmin? Or F-Zero? Things would be too unpredictable to just simply take the risk.
Sure, I don't think Nintendo loses anything by becoming a third-party developer, and I'd actually embrace it, but they're in a confortable zone right now and they have no inmediate need to ever think about that.
