For Pokemon I would love to see set lists for the first 151 pokemon.
My favorite of course tho is Snorlax, so maybe him next 😉 haha
Even if it starts out as just the first few years that have cards for that pokemon, say all Snorlaxs from 1998-2006 and then slowly the newer sets with a snorlax card get added later on that would be cool. Some pokemon only appear in the TCG a few times too, like Kadabra, so a set for them could be easier for example.
I would also love that these sets combined languages too, as not every langauge gets every artwork (japanese exclusive promos etc) but people still like to collect at least one of every unique artwork for a pokemon.
And lastly I would like to see Japanese Pokemon sets added as well. Feels sad right now that all of my Japanese cards have no sets.