I think, given the way the game has evolved so far that removing classes entirely might not be a bad idea.

If the game had evolved where class combinations might lead to multiple different ends/jobs then the class system might have been worth further developing (for instance if AST had had a solid requirement of CNJ30/THM15 against WHM at CNJ30/ACN15) ... but given the development trend towards independent jobs ultimately dispensing with classes and rewriting the class stories to jobs is pretty much inevitable.
Cross class skills are getting revamped - I hope for details on that soon; and that will provide more clarity going forward.