An idea for modifying Descent: Journeys in the Dark 2nd Edition, allow players to purchase skills from any class. You still choose 1 class as your starting class for determining your starting skill and equipment. You can purchase other starting skills (no-cost skills) for 1 XP.
Your archetype is the archetypes of all classes to which your skills belong. For instance, a character with both Hexer and Disciple skills would be a Healer-Mage. This means that Overlord cards that have extra effects vs. particular archetypes get a bonus for either archetype.
Additionally, if a hero party uses these rules, treat the party as having 1 additional hero above the number they actually have. (The party maximum should be 3 heroes, treated as 4 when using these rules.) This is to prevent the flexibility from overwhelming the Overlord, since the conditional card benefits are likely not enough to balance it.
EDIT: I'm tempted by the idea of making a PB system for attributes, health, stamina, speed and armor dice too, and with a mix-and-match pool for Heroic Abilities and Heroic Feats. Anyone else want to help me compile all the existing stats to find a best-fit formula for costs?
EDIT 2: Okay, so I have a tentative PB method. Anyone familiar with all this is welcome to jump in, as I know I still haven't really taken into account armor dice. Mathematically, a PB is actually somewhat problematic in that certain archetypes have higher total statistics on average (appearing to be Warrior > Scout > Healer > Mage), but you can get at least a decent approximation. As for armor dice, these are also typically actually balanced not by other stats but by Heroic Abilities anyway (compensating with a bonus die in certain circumstances, or similar).
Anyway, here's the rough system:
Creating a Hero:
Each Hero starts with the following:
2 Speed
8 Health
3 Stamina
1 Discipline
1 Might
1 Knowledge
1 Awareness
1 Gray Armor Die
12 Hero Points
You may exchange each Hero Point for any of the following:
+1 Speed (max. 5)
+2 Health (max. 14)
+1 Stamina (max. 5)
+1 Discipline, Might, Knowledge or Awareness (max. 5 each)
A Hero must have a score of 3 or more in at least one of Discipline, Might, Knowledge, or Awareness. A Hero may not have a score of 1 in more than one of Discipline, Might, Knowledge or Awareness.
Once all Hero Points are exchanged, select one Heroic Ability and one Heroic Feat. Your Hero gains that Heroic Ability and that Heroic Feat.