I have been making new PCs start at level 1 with 0 xp as Gygax intended. So far, so good but I am thinking of the future when players start hitting levels 6+. Since the soul of a good game is player agency, I believe that planning and resource management should be able to mitigate the inevitable disasters that strike adventurers.
I have considered allowing players to "bank" experience points for their next character. Basically, a player can spend gold on a 1gp for 1xp basis that goes towards their next character, perhaps an apprentice, henchman, or heir. I like to introduce cool and useful things for my players to invest in; choosing to bank xp means a player misses out on something desirable. While this sounds decent enough in theory I suspect there will be unintended consequences.
I am open to feedback, criticism, and alternative ideas. If someone can make a good argument I am even willing to concede that players should just start off at level 1. I will channel my inner grognard and plainly state that I don't like milestone xp, starting off new characters at the lowest level in the party, or rulings that turn character death into a mere speed bump on the road to high level play.