Yeah, some new characters would be nice if they were to re-release it on the Switch. Inklings, Spring-Man, maybe even Captain Toad or Cranky Kong would be some great additions. I also really liked the idea of them integrating all the 3DS content as well since the Switch is a hybrid console. Would definitely help beef up the overall product. Though, the longer they wait to get this port out, the more pointless it seems. Might as well just start working on a new one so we can see what the Switch can really do.
They should have done the same with Mario Kart given they made some very significant changes that would have benefitted a sequel. Otherwise, the tracks are just so been there done that.