Hey Prof. Blue. Saw you in Jugg a bunch recently. I'm Mach/No. Six. Had a feeling you were someone's alt.
I think having a solely skill-based build making system would definitely be interesting. The current concept of classes is extremely limiting. There are only 6, yet the number of builds you can make is so few it's painful despite that they each have 12 skills, due to the fact that (1) classes generally prevent skill synergy since the skills they have are essentially arbitrary and (2) half the skills on every skill tree are (at this point, almost purposefully) left unviable for any build in order to keep the class as a whole balanced.
I have always thought it would be a lot better to have a lot more classes (like 50 or something) but each with only a couple very distinct skills that were intended to work together like in AQW or Dragonfable (although their classes have way more than 12 skills). In a way, that's how it was kind of like back in Beta, when the level cap was way lower so skill points were actually limiting. Most people just had 2 skills maxed and that was their entire build, but those skills went together and it created something distinct, especially since there were no energy regeneration skills at all.
At this point, I do think it would be unfeasible to break the class system entirely. But I would be very interested in re-doing the skill and skill point system. I really like your idea of tiered skills. Right now we have 4 level-based tiers (level 1, 2, 5, 10), but I was thinking maybe we could have twice or three times as many tiers for each class, all the way up to level 40. Of course, we would need to invent a bunch of new skills to fill them. The caveat would be that you can only choose one skill out of three to unlock in a tier and that might influence what you can unlock in the next tier like the way it currently is. At the top of the skill tree, we would have the fundamental skills that define the class like their passives, and near the bottom there'd be much more interesting stuff that caters to very specific builds. This would make it so builds and classes are much better defined by what skills they have. That might be crazier than what you're suggesting, but yeah, I'm up for the idea in general, even if there's little chance anything of the sort will ever happen.