Add a Fox Type.
Then remove every other type.
I'd probably revitalize the combat. I get the tried-and-true formulaic aspect of pokémon is one of it's pulling points; You can go back at any time after playing one game and more or less still know how to play it, or learn it quickly and intuitively.
However, I feel like this medium lacks strategic depth; You can argue competitive, and yes, competitive is strategically superior to the games, but the thing is, it shouldn't be for a game whose main focus is PvE, single-player content. The fun and challenge from pokémon should come from the game itself; I shouldn't have to seek a third party to truly enjoy the full potential of a game's combat system, especially when that's only one part (albeit a big part) of it.
Meanwhile, how much of that strategic depth could be achieved by changing the combat from turn-based to a more action based battle system, with a higher focus on mobility, usage of terrain, dodging attacks, alongside things like type advantage?
A rock type might be stronger than an electric type, but if the electric type can dodge every single attack - Say, a level 100 Pikachu, fully trained for speed and with agility (getting like 500 speed or so) versus an Onix trained for defense? The Onix is considerably bigger, has sweeping moves and stronger attacks, but it's also considerably slower. Isn't it more consistent to imagine a faster pokémon would be better at dodging said attacks, and whittling Onix down slowly - Or using terrain to it's advantage by finding and striking out of cover, given that it's considerably easier to find a place for a Pikachu to hide in or behind than it is for an Onix - than it simply getting one hit in, getting smacked, and getting knocked out?
Pokémon would work a lot better than it currently does in a medium that gives you more strategic diversity than simply moves and stats. Pokémon Reborn tries to medicate this through field effects, and while it works to a certain extent, I can say from firsthand experience you can disregard the system entirely and still breeze through the system if you have a simple enough understanding of the mechanics and teambuilding.
It'd also be more interesting if more pokémon had unique moves - And I don't mean moves like Dragon Ascent, which are simply existing moves given a new type, a new animation and a new name. I mean each pokémon having an aspect truly unique to it and it alone, and it making all pokémon being more unique.
Yes, that'd be pretty difficult to make for all thousands and thousands of pokémon we have, but given that the total amount of combinations you'd get from pokémon types is circa 324, do we really need that many?
So, yes. Size down, make each character more unique through something other than design and name, and make combat a bit more active and more rewarding strategically.
Now excuse me while I get myself some fireproof clothing and extinguishers.