The problem with that idea is that it's easier said than done. A complete overhaul of all the rules and mechanics from the group up would most likely require a complete overhaul of all the codexes at the same time. Such a venture would alienate a large chunk of the player base while simultaneously costing a huge amount in both resources and manpower. Although, if rumors are to be believed, we'll find out exactly how well that's going to work out when WHFB launches 9th, which is expected to be a complete overhaul and major trimming of the factions.
Well are you talking niche or are you talking Force org? CC is a niche role, Fast Attack is a general category. Jet bikes don't really compare to infantry, and on top of that you're paying more for them. I would expect a unit that I'm paying more for to be better than a unit that I'm paying less for, which is kind of what balance is.