Advancement System Before Action Resoultion Mechanics

The other day, Jeremy sent me a file for a Supers RPG that he's working on. He wants to play test it, and I'm looking forward to that. He's going for a rules-lite system, so he's trying not to bog it down with too many subsystems or overly define what any particular superpower can and can't do. That's fine. 

He's got an interesting action resolution/combat system. It's 2d10 based, but you add attribute scores (your superpowers or skills) as appropriate. If you roll snake eyes, you auto fail. If you roll any other doubles, the dice explode and you keep rolling (but snake eyes on a further roll is still auto failure). That's interesting and I want to see how it plays out.

Character creation has lots of d% tables for determining things randomly, but he also says that picking and choosing to fit your idea is fine as well. The only problem I found with this is that the big list of Attributes (again, the super powers or advanced skill-sets that heroes have) is a 3d100 chart. If you're picking the abilities that you want, no problem. If you're rolling randomly, this will skew heavily into the middle of the alphabetical list of 297 options. I checked the dice probabilities, and you're 7500 times more likely to get item 151 (or 152) than to get item 3 (or 300). Of course, with nearly 300 entries, it's still only a 0.75% chance (each) to get 151 or 152.

And what do you know, when I rolled a random PC, I got Leap (entry 151) as one of my rolls.  

So there are a few things to work out there, but nothing major. 

The big problem is, there's no advancement system. No way to earn XP or additional Build Points (once you determine your powers, you can set their strength with build points, then add features or limits plus or minus more build points) after play starts. There's no goal of play other than "play out stories like in comic books" which seems like it will only be conducive to one-shots/convention play. 

I think that anyone designing an RPG should figure out what the advancement system is before trying to figure out the resolution mechanics or char-gen features. You've got to know what the players should be doing with their PCs before anything else. Otherwise, what's the point of play?