Reserve Hero system

[Marth2Vorg]

I have a campaign that has four heros, warrior, mage, ranger, and summoner. But each level your only allowed to pick two, (example: Ranger and summoner.) Then how it works is that if one of your heros dies, (example: Ranger dies) your forced to pick one of the heros you didn't choose, (Warrior or Mage). So on and so forth, basically a reserve cache of heros. I have figured out a sort of functioning tavern that works for now, but I'm hoping for a dialog or circle of power option. Anybody with any advice or walkthrough would be appreciated.