ARPG: like the D20 sytem with no profession/class

It doesn't look to me like it really gets rid of class (though you are decreasing the number of classes to 4), now you just have becoming a wizard/sorcerer etc.. cost XP, and you aren't calling it the same thing, but you still have what type of character someone is linked to their BAB, and hit points. If you really want to get rid of class let people buy their BAB, their spell-casting abilities, and their hit points separately. You still end up getting something that resembles the classes in D&D potentially (a person could buy the BAB, hit points, and spell-casting abilities that a Sorcerer would have) but at least that way it's not like you are just getting pre-packaged classes in a different way than you would in standard DnD. That and having to buy the ability to even use spell-casting abilities, along with lower HP, and weaker BAB pretty much amounts to giving a sorcerer/wizard type an XP penalty, are they really powerful enough to warrant that? You do give them better hit die than they get in DnD (well better than arcane spell casters do anyhow) so an XP penalty for them might be ok.
Anyways if I were making a classless D20 system (and I sort of am, but it's very different than what you're trying to accomplish) I would get rid of linking spells/expert abilities or whatever to HP and BAB, and just have all those things bought separately. I would just make spell-casting etc... cost enough XP that there's no need to take an additional penalty to your BAB and HP.

Anyways you might want to actually post this on Wizards forums, and get some input from people whom are really into D&D and making D20 house rules (they have a whole forum for house rules I'm almost certain).