There are a couple of things I'd love to see for WFRP that would work well with the print on demand systems used with the Death Angel expansions (played a 6 player game of that last night and we won woot!).
- Additional basic action packs without having to buy a complete players box
- Standard item cards, I would LOVE being able to give people cards for their normal weapons and armour too.
- Errata packs, I'd pay for a pack of all the errata'd cards so far (though I do LOVE the one with 'This is where the requirements go' it's grand.
That's just off the top of my head, but if there's a game that could really work well with Print on Demand it's WFRP.