I like the idea of this a lot more than I thought I would (as someone who is, in fact, tired of "Multiverse" stuff).
I think it would be really cute if it was a "spiritual successor" to Captain Rainbow, in a way. Or something like an Epic Mickey for Nintendo stuff, to use another example. Something that focuses almost entirely on forgotten Nintendo franchises and characters. Mario goes to various worlds (Mole Mania, Panel de Pon, Gumshoe, Yuyuki, Odama, Clu Clu Land, Custom Robo, etc.) to help them out.
Now, maybe that wouldn't fly for the next big 3D Mario... I'd buy it, though.