A little more detail about my post from yesterday.
First of all, Stables of PCs. The idea is that each player will have two to five* PCs rolled up before game time starts. That way, if one PC meets an unfortunate end, a replacement can show up on the spot. Also, sometimes a "specialist" might be needed for certain missions, so a player might opt to run one of the "backup" PCs instead of their main PC.
The drawback is that players need to spend more time creating characters. Luckily, with Classic D&D as a base for my house rules, that doesn't take too awfully long.
What I'll do for XP is this - whichever PC a player uses for a session gets full XP for that session. All other PCs in the Stable will gain 1/3 of that amount. Imagine that Player A has four characters in their stable and Player B has only two. Each selects one of their PCs and they delve the megadungeon successfully, earning 900xp each (to keep the math simple for the demonstration). Player A has three characters in reserve, each of whom will receive 300xp. Player B only has one reserve character, who also receives 300xp. Let's call it "downtime XP." Fairly simple.
Like I said yesterday, I plan to use an XP Bank. If a PC dies, all the XP that character earned up until death goes into the Bank. If a PC gets hit by an energy drain attack and loses XP, again it goes into the Bank.
The main purpose of the Bank is to be able to create replacement PCs that won't be too far behind the other characters in a party. Also, I feel that players earn XP, they should be entitled to keep it. When a player adds a new PC to their stable (one with 0XP), they can withdraw as much of their banked XP as they wish to give to the new PC. Yes, that means a player with a lot of banked XP might be able to create a replacement of a higher level than the one that was lost. So be it, they earned all that XP previously.
Now, things get a little tricky when factoring in our group's practice of awarding 100xp bonuses for pictures or session reports. With my Bank idea, doing these things would be the only way to transfer banked XP to an already active character (one with 1xp or more). Using the above example, Player A draws three pictures of the adventure. The PC that Player A used earns a 300xp bonus. Player A could choose to distribute up to 300 banked XP to each of the three reserve PCs. But let's say Player A only has 500xp in the bank. Then he can, if he wishes, divide that 500xp among the three reserve PCs as he wishes, or leave it in the bank.
One final note - bonus XP from pictures, and Bank withdrawals, will not gain any Prime Requisite bonuses. The 1/3 granted to backup PCs from an active PC should be calculated before that PC's Prime Requisite bonus, if any. If any backup PCs get a PR bonus, they gain the bonus on the "downtime XP."
Hopefully that all makes more sense. But I have a feeling I went on a ramble.
*Today, I'm feeling maybe 5 is too many. I may limit it to three or four. I'm still working out the details of how I want to run this thing.