I have read someone pointed out Skellige faction will have problems with adding cards since they are minor in the world and aside from Witcher 3 and few places in the books they don't figure much, but imagine the problem with Touissant how do you get 150 cards from that.
Nice solution would be expansions for the current factions. Nilfgaard gets 20-30-40, idk, cards all themed around Touissant with some new mechanics, maybe new leader as well, NR get simillar amount themed around Kovir and Poviss, Scoiatel gets the pack called the Sympathizers or something themed around non-humans living with humans and not being in armed rebellion but who support non-human rights struggle and Scoiatel, Monsters get say Draconid themed expansion, vampires are already too present to constitute major expansion and they already have a leader, but some evil dragon guy CDPR just made up or Vran or something could be fitting leader, as for Skellige, just invent some king with his own trademark way of war or even if they are already very present do something themed around Druids or Beserkers. There could be more than one of this expansions for each faction over time.
As for Zerrikania and Ofier, they can hardly be full factions, and it would be stupid to combine them, they are on the opposite sides of the world and while there could be thriving interaction on the Witcher planet equivalent of Pacific, that is never claimed or hinted so it would be huge stretch, besides those are very distinct cultures, it would make as much sense as combining NR and Nilf. Stuff related to this exotic realms could be incorporated in neutral cards, like witchers and their potions and abilities are. So expect Azar Javed gold card in the future.
Variety will grow over time, but don't hope for serious overhauls like separating witchers and their stuff or sorceresses or vampires or Wild Hunt or realms within North, it would demand whole slew of rebalancing that no one needs. And it would make reset almost certain. So before asking for serious rehaul which would be biggest rehaul since Gwent took stage in Witcher 3 ask yourself do you want a progress reset, because that is how you get a progress reset.
But hey just my two cents it is up to developers in the end and no one can blame them if they are not willing to seriously upset the balance they have long been working hard to achive just so we could have another faction of knights or some exotic stuff not even regular fans of the games are that much interested to play with.