First of all, Pokemon won't have an upper limit.
Only different talent, so yes if trained for long enough a ratatta could become strong as God AKA Arceus.
And although i am a huge pokemon fan, Its been a long time since i've watched the anime and could get some things wrong.
The mc won't have any kind of system only the power of sunshine the same as Escanor from seven deadly frames.
No, the drawback won't be there but he can burn his life force for more power.
And the chapters will be kinda short so bear with me.
I am not creative.
If you want the MC to catch any pokemon do let me know if i like it i'll add it.
The MC will be travelling all around the world, yes he will be reincarnated.
And no he will not catch every pokemon, He will build bonds with the pokemon who chose to follow him.
And yes he can and will catch legends.
Try and guess witch legends he will catch.
He will be a pretty laid back guy but won't tolerate disrespect.
He won't hesitate to kill if someone hurts his pokemon.
Some pokemon will have custom ablities.
Cuz well..... why not?
Other people will also have custom ablities pokemon.
And yes he will carry more than 6.
Actually way more than 6.
Spoiler Alert.
His starter will be a shiny froakie.(Battle bond)
Although he will start in Alola.
Yes, Ash will be 5 yrs old when he is starting his journey.
And comment here on who you want the romance partner to be.(Don't be weird plz)
I will pick the most liked comment to be the FMC.
And Mc will be catching a gastly cuz my boi gengar.
Will also be shiny cuz Mega gengar white shiny go brrr.
And yea thats about it, i will add more info as the chapters progress.