Okay. Let's try to break that, theoretically, for just a moment. A theory states that the smaller your army, the more powerful. Assuming that's completely accurate (it's not, entirely...), the optimal army by anything we describe would be half the army made up of CR5, followed by two CR15s, which is the smallest it can be made. That's a mere 22 unit army... more of a squad, really.
Under the system I described above, which granted, is considerably more complicated to work with...
A CR15 creature requires 225 support units and 225 points for itself. 225 CR1 = 225 points, meaning that you could then have another CR15 creature with another 225 CR1s. If you wanted the support units to be CR2, well... you couldn't. You'd have to mix it up, since 225*4=900, and you've already spent 225 points.
I think the optimal system as such would be to have larger numbers of slightly higher CR units... to average out your amry level a little more... which isn't to say that single powerful units wouldn't be useful, but it all depends on how you use it. Don't forget all that gold either... assasination gear could probably be contrived that makes single units VERY risky indeed. Insta-kill spells exist, remember... and Ressurection is not available.
On the other hand, having some players have armies with higher powered units, and then combining forces with teammates in coordinated strikes... well, that's strategy and tactics, the sort of thing the game is going to be about anyway.
But again... thoughts?