That's a good idea, thanks. The game this core mechanic was taken from has a Momentum/Karma mechanic where characters earn 1 Momentum on each full success. 3 Momentum turn into 1 Karma and characters can have a max of 3 Karma.
Karma can be spent before the roll to:
- Decrease the difficulty die (no lower than d4)
- Increase the attribute die (no higher than d12)
Karma can be spent after the roll to:
- Avoid taking strain
I really like that mechanic and it's fun at the table, but there's quite a bit of record keeping involved AND it was way too much to explain in this one page pamphlet!
Perhaps I should create an addendum of optional rules and put that in there (along with the 2 attribute die when the role applies if you'd allow me to use it).