Purchasing levels with experience

[Citizen Joe]

I checked over in the RAW questions thread and they suggested posting here in homebrew.

I've been considering purchasing new levels with experience rather than automatically getting them when you reach certain experience point levels. The basic formula would be [Current ECL X 1000 xp] = xp cost for new level. I've already seen variant rules on reducing level adjustments for monster characters, and those 'spend' xp as well. Plus the use of XP for magic item creation. On the surface this doesn't change anything, but I'm more interested in how this could be abused.

I'd recommend keeping track of Total XP earned as well as Current available XP. Perhaps even a log of how the xp has been spent.

One use of this might be for level loss from death. If you were within a thousand XP of getting your next level, then died, you could spend the appropriate amount of XP and get that lost level right back.

Another abuse may be intentional sandbagging to try keeping your encounters low, but that assumes the DM is going to play fair when you clearly aren't.

Possibly one could hoard xp enough for multiple levels and then bypass the multiclassing penalty...

Anyway, let's hear your abuse of this system so I know what I'm getting into.

[InaVegt]

It's already allowed to wait with leveling if you have enough experience, just say your unspent experience has a max of (Current ECL X 2000 + 999) and you've got a completely different mechanic for the same thing.

[Citizen Joe]

That seems to work... maybe this is a better formula:
Max reserve xp = [ECL x 2 +1] x 1000 - 1

That puts you at 1 xp short of a second level. And I guess there would be an XP penalty in that anything beyond your reserve limit would get wasted.

That also solves the problem of a 'lucky' first level character killing a dragon and suddenly jumping to very high levels.

I'm liking this option, especially since it solves alot of those "How far did that level loss drop me?" questions.

Is there a magic item that 'gives you levels'? How would that come into play?

EDIT: Deck of Many Things artifact can drain 10,000 xp or grant 10,000 xp. Granting is easy, but the draining... can you have a negative xp reserve?

[Erk]

check out the alternate XP buy rules in Unearthed Arcana: I think they're similar to what you are talking about and come pre-balanced. They don't seem to be on the SRD but they are in the back of the UA book.