I think the alphabet idea of the Unown is good enough and doesn't really need changing. I didn't think a "!" version should have been added but I guess it added a bit of creativity to the species.
The one thing that I have given a bit of thought to in the new games are the starters. Since Pokemon Gold, Silver and Crystal, the starters' evolved forms have always been dual-types. This, in my mind, takes out the "purity" of the starters because they're supposed to be your first Pokemon - rare and pure fire, water or grass types. This isn't really a huge deal, however, I want a trio of starters, like in the original Gold, Silver and Crystal with pure fire, water and grass typing. It just makes the whole starter experience more.. well, whole.