Disclaimer: I'm not very knowledgeable on the world of Pokemon but I have recently read a Pokemon fanfiction and I thought this idea would make for a good fanfiction.
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Short Synopsis:
A Pokemon fan died and woke up in a different world. He woke up in the world of Pokemon, as a Pokemon.
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The whole premise of the story is that the MC goes from being a lvl 1 Pokemon, all the way to becoming the strongest one, even surpassing the creators.
I don't have a clue what Pokemon you should choose for the MC to reborn as but you should give the MC telepathy so he can talk to Pokemon and Trainers.
Have the MC help in the original plot of Pokemon and also have him challenge the Legendaries and later on the Gods.
You could give the MC a cheat ability like Unlimited Potential so he would actually be able to surpass the gods eventually.