One idea I have seen was called
P6, where you take a standard D&D/Pathfinder character, and after they reach level 6 they never gain any more levels but instead just get additional
Feats (aka special abilities). I'd also want the player to make a record of the hit point rolls during their leveling up, so whenever they get a new Feat, they also get to re-roll one of their hit die rolls.
I.e. at level 6 a Rogue used a d6 to get hit points, and their current total hit points is 23 hit points. Hit points for the first level are maxed out, no Constitution bonuses, and the successor levels are 3+5+1+4+4. The character gets enough experience to gain a Feat. The player also chooses to re-roll the hit points they got at 4th level. They roll a 3, and their new hit points are 25: 6+3+5+3+4+4 (re-rolls can never reduce the hit points). If the character later chooses a Feat to get a +1 to a stat and that lets them get a Con bonus to hit points, it would again give them a bonus, but one at a time. So assuming the Rogue takes a Feat to boos their Con, so it gives them a +1 bonus, they reroll the hit die for their 2nd level (the first level is already maxed out). They get a '1', and they have 26 hit points now: 6+3(+1)+5+3+4+4. Even though the d6 roll was less than what they had for 2nd level, the original roll of '3' was kept, and they make a note that they got +1 hit points from Con bonus for that level.
These additional Feats would be used to get more skill points, spell slots, Special Ability uses, better Saves, etc. Figure anything that would normally be gained via levels would instead be gained as a Feat.
Instead of taking a Feat you could replace a character class with a different class, one level at a time. So a
Commoner/6 manages to gain a level. They have had access to schooling, and choose to replace one of their Commoner classes with an
Expert class. So they now look like Commoner/5 & Expert/1 (likely changing their first Commoner level to take advantage of the hit point bonus).
This could be used to give lots of special abilities to David and Alice, but they are still the relatively weak humans.
Still, with Astun's aid to boost them, how much additional magic was left in them that Astun can use to watch their adventures? Not quite the level of a
Truman Show, but more along the lines of the Survivor tv series, where David & Alice are encouraged to deal with various challenges for the entertainment of the various mages and deities.
Good deity: "Hard to believe he outsmarted you like that, right?"
Evil deity: "He didn't out-smart me, I just wasn't ready for him to out-stupid me"
Good deity: "True. It took me five clues just to get his attention."
Evil Deity: "Now that was funny"
And the whole time Astun is charging scrying fees
