(This plan could be generalised to other formulae as well)

The current experience-to-next-level formula is the same for all heroes in all games. It is described in more detail here: What is the formula for how much experience it takes for a levelup?

First Level: 30 exp
Each level after that: previouslevel * 1.2 + 5  (rounding down)
With a maximum requirement of 1000000 (at level 55)

[edit] Proposal

Create a simple formula editor in custom that allows you to customize each of the constants in the standard formula.
- First level (default 30)
- multiplier (default 1.2) (should probably store as 1200 but display and calculate as 1.2)
- add-per-level (default 5)
- cap-per-level (default 1000000)
Store customized formula in GEN
Give each hero an optional customizable formula which can be used instead of the default formula. Store in hero data
Add a visualization tool so that game authors can see a preview of how many experience points will be required for each level

Do we need to add any constants to this formula for better flexibility?

[edit] See Also

bug 110 - Make various formulae customisable
Scripts:Custom experience to level formula - a script which fakes a custom experience-required formula