|Flat the Impaler|
Sorry for reviving an older thread, but here's an out of the box (and also completely untested) idea:
Instead of (or possibly in addition to) trying to expand the character decks to fit the characters, what about expanding the characters to better fit their decks?
Introduce a new dual-sided "Class" (or Multi-class, or whatever you want to call it) card type that represents some of the basic skills/powers of that class. This would be a completely optional upgrade option.
The intent is to impart the flavor of each class, but not all of the power or full access to another character deck. You could gain a limited number of cross-class powers, skills, and cards. You could gain the skills/proficiency requires to actually use cards in your deck. You could even help Flenta realize her dreams of becoming a spell caster!
How to acquire:
This card type could be unlocked using a Card Feat, which then allows that character to display their new Class card next to their Character/Role card, adding its traits, skills, powers, and card feats to your character.
To try to keep it from being a huge power jump, the initial benefit of the card would have to be minimal: 1 additional skill with no/small bonuses, and a rather limited class power.
The rest is up to you to unlock with feats. This would allow for a lot of flexibility in building your character and in distinguishing the same character from player to player.
The front of the card:
There would be 1 (maybe 2) specific class skill already unlocked (ex: Arcane: Int; +0 or +1 modifier).
A very limited number of Skill feats available, let's say 3:
1) a +1 to that class's primary base skill (Str/Dex/etc)
2) a +1 to another a secondary skill
3) a +1 or +2 to a specific (Arcane/etc) skill
These would add to the skills on your character card. For example, if you had 2 skill feats invested into Str on your character card, and you invested another skill feat in Str on your class card, you would have a total of Str+3.
Also very limited class-specific powers, and a limited number of Power feat upgrades (maybe limited to 2 or 4). For example, the Cleric's "Reveal Divine --> Heal" could start off limited to Blessings, and could be upgraded with a power feat to "Blessing or Spell".
The back of the card:
Taking a Card feat on (but not to gain) a Class card would still increase the size of your character deck, but it would also grant you the ability to add these extra cards from this specific class deck. The number of card feats would be limited as well (let's say 4: 2 of 1 type and 1 of the other 2). For example, if Kyra (Cleric) had a Fighter Class card with a "Weapon 1" checked, she could add this weapon from either the Cleric or Fighter class decks, but could have no more than the 1 Fighter weapon in her deck.
A quick blurb about the class in general.
How to distribute
This could be made available as a (free?) download, and players could print out whatever class(es) they wanted. If done this way, the only other thing you would need is whichever class deck(s) with which you wanted to multi-class.
Prestige class, anyone?