The Crimson Binome
Hero
Going from level 15 to level 16 requires thirty thousand experience, according to the chart I found, but the actual benefit of that extra level is pretty minor for most classes - both fighters and rogues are looking at an ability score improvement, where they have probably capped their prime stat long ago. Instead of gaining level 16 in fighter, a character could gain 7 levels of wizard (24k) and five levels of cleric (6500).What if instead of experience being a static number you had to spend it to gain a level in a class, and then the experience points to level up can be applied to each class seperately.
So the first level in a single class costs 300 (?) XP, no matter how many other levels you have in other classes.
What problems can you forsee coming from this?
Even if you don't get extra HP from those levels (which you really shouldn't), the ability to cast fourth-level wizard spells and third-level cleric spells is probably too much of a benefit to gain in exchange for ~10 HP and +2 to Wisdom.