I think they should just introduce all the other types that are in the game but not in the TCG like ice, poison, flying etc. These should be secondary types symbol and just sit beside the main type symbol. I know some pokemon have their main types as those not in the TCG at the moment, but they will have to stay as a secondary type.
Weakness and resistance should stay the same otherwise it could get complicated. Then have effects of those second types come into play like other types sometimes do. eg, said effect of example attack - If the defending pokemon is ghost type this attack does nothing.
This way the 2nd types come into play but don't have extra burden on the game play other than attack effects and perhaps abilities as well, no extra type energies needed.
Or is this too complicated? Sorry for long post.
Weakness and resistance should stay the same otherwise it could get complicated. Then have effects of those second types come into play like other types sometimes do. eg, said effect of example attack - If the defending pokemon is ghost type this attack does nothing.
This way the 2nd types come into play but don't have extra burden on the game play other than attack effects and perhaps abilities as well, no extra type energies needed.
Or is this too complicated? Sorry for long post.