I agree, we should have something to the nature of Poffins or Pokeblock, I think that they were both very useful. (I'd also like contests to go with this, but I don't see it happening. Contests was a big reason why I wanted a Gen 3 remake.) An Underground world be great, but I don't see it happening, I think it'll always be a Sinoh exclusive. Though I could see something along the lines secret bases like in RSE.
I'm really excited for the easy visibility of IVs and EVs, hopefully we'll be able to see what our Pokemon has. That's one mechanic I'm really hoping for.