1) In line with game difficulty, have the innate "immortality" of champions be toggleable during game setup. Some games can have the currently proposed "immortal" champions, and some games happen where champions are totally mortal and death is death.
1a) Can the immortality be researched?
1b) Can the injuries be a little more severe but treatable? Perhaps forcing the player to decide should they take their champion turned damage goods and place them in the betty ford clinic for X number of turns, with the promise of healing a minimum of Y number of injuries and a max of Z injuries?
2) Whether or not the immortality is configurable, i like having decisions I need to make about my champions. In MoM (sorry, I use Master of Magic as a reference point because I still play it) one of the coolest choices was whether or not to even send Champions out of the home castle. Keep a (most) champion(s) at home, get a boost in magic (which during battles could be a really big deal). Send a champion out, get way more experience for the champion and have the champion cast spells from a separate mana pool (but have only a select amount of spells to cast). During combat, if it looks bad, teleport the champion back home via the Recall spell which everyone had access to as part of arcane magic. If a champion dies, resurrect them with a spell. The resurrection spell was kept in check because:
a) Unless you already had insane casting potential, only your wizard could cast the spell, and that would eat their casting of any other spell for X number of turns.
The majority of Champions (other than Torin, see below) hurt to lose, but they really _could_ be replaced. The champions were graded. As the game went on, level 1 champions became available that were better than level 2 or 3 champions from the early rounds of the game.
And since I'm referencing MoM, it's nice to see this thread addressing the infamous Torin problem, or rather, "Why be any other form of wizard other than life wizard?" I can't count the number of games I played even on Impossible level where, if I could pull of summoning Torin, I could, with a single model, walk around the map destroying anything in my path. Torin and some squads of dark elf sorcerers with doom bolts. It's fun for a while, but gets boring quickly. If _all_ champions were like that, I probably would have gotten bored with MoM.