I've always thought that PP has a lot of potential using cards as customization tools. Here are two examples:
"Nemo, the Firefly is great, but what we asked for was a cheap Lancer without an Arc Node... can't we at least have our old Talons back?"
- Archduke Runewood
PP is already doing this with the Jack boxes, where you buy a chassis and are able to turn it into one of several configurations. It would be great to be able to have system cards, where you could pick your own chassis and customize its weapons.
PP already has something similar with Grind, which was very limited as a boxed stand-alone game, but proved it could be done.
"Really? Another Arcane Bolt drill?" [rolls eyes]
- Journeyman Warcaster Rhodes (before being expelled from the Academy)
Custom spell lists (complete or partial), custom abilities, custom weapons, mark-off effects (like Paymaster), the sky is the limit.
I know this could bring total chaos to the meta-game if done wrong, but it could be a very interesting route for future development.