AbdulAlhazred
Legend
I really like the idea of the cards also having a weight - so you play two cards: one as effect, and one as weight (I really have to find a better word). That would work with a one deck game...
But I'm still holding on to the idea of two decks for now - there's a picture starting to form in my head (and there are 2 different card types in it )
- 20 power cards and 20 weight cards (numbered 1 to 20)
- you draw 5 cards of each type
- you play 4 rounds
- you shuffle back [encounter] and [at-will] power cards into the deck after every round
- you shuffle back your weight cards after every round
- you're only allowed one [encounter] type card per round (if you play 2, the second one is void)
Not sure this would really work (pretty high variance) - but you get a "d20" of sorts, an AED thingy.
Now all that's left is creating 20 cards for every class! Pfft! Easy peasy!
Eh, now see, I'm not so sure I want to emulate d20/4e with it, not THAT closely. I'd rather see it as somewhat of a strategy game of its own. That is, what do you play and what do you hold onto? There might be an inducement for playing the 'lower value' cards. Maybe you simply get a specific mix of different values, depending on your level (etc). So the equivalent of an 'at-will' is a card you can have say 8 of in your deck, but it they have a modest effect/weight.
Another option is cards each have an inherent weight, but they they are offense/defense values. So you can play something that is heavily offensive, heavily defensive, kind of a mix, or etc. Maybe specific special cards have better values against certain other types of cards. Again, you could have 'kickers' and 'counters'.
I'd say that your deck has to last you the encounter, though maybe some cards are 'daily' and can't be shuffled back in until you get a long rest or something like that. OTOH I'm not sure you need that mechanism, a card that makes up 1 in 40 of a deck would be hard to rely on, and come up relatively rarely, but would still be a big signature move. Obviously you'd have to consider your cards to be more 'plot coupon' than indicators of some option you always have. You could play that up in card design too.
Maybe there could also be 'fortune' cards that would be a type of, or the main type of, kicker that you could drop, that might supply the function of the 'weight' card as you've described it. So you can build a character with few different moves, but a lot of fortune, or one with more moves and less fortune.
I could definitely see this kind of thing working well for say a 'swashbuckler' kind of game where PCs duel and do lots of crazy stunts and whatever, and the plot is heavily extemporized during play. Cards would let you pull stuff out of your hat. "No! I'm not run through by the Count's Blade, I play 4 fortune, he's disarmed and I flee!" Very much like other diceless systems that use some sort of currency for that kind of thing.