I was thinking the other day - I kind of want to start a game around the 2nd level range. But I was having trouble settling on the precise XP number. If you start at 2000 to get fighters to 2nd, MUs are only 1st. If you start at 2500 to get MUs to 2nd, thieves are already 3rd. So picking a single ideal numerical solution is hard.
It is also a little weird when all the PCs start with exactly the same amount of experience. We already admit significant variation between PCs in terms of ability and starting gold - why not XP?
3d6 * 200 starting XP seems like a promising amount, averaging just over 2000, and never high enough for a fighter or MU to hit 3rd. The interesting question is whether you roll it before or after committing to a class. If you let it inform class choice, then you might get some interesting choices, where a stat line which is otherwise mediocre for a particular class gets played as that class because the XP roll is good for it (like low int, high XP to MU) or even worse otherwise (like a low XP roll where you can get 2nd with thief or cleric but nothing else). I suspect that taking a high XP roll and using it for thief 3 instead of MU 2 or fighter 2 would probably not be a frequently-chosen option. So this might be a great way to get a pretty consistently 2nd-level starting party, outside of very low rolls that don't even crack 1200.
On the other hand, a simulationist argument in favor of rolling XP after choosing class might be that it would be weird if nobody ever started a 1st-level MU. Although maybe if you roll less than 1200 XP, where you're at 1st regardless, maybe MU becomes a real option again. One sleep per day is one sleep per day...
(And then once we're rolling starting XP, clearly we need some rules for risking terrible injuries in chargen in order to potentially gain more starting XP...)