I recall that someone did exactly that for Dragon Rampant and posted extensive reports here a few years back. It seemed to work just fine. Mechanically, the game will be just the same (give or take the odd interaction with terrain).
I've played quite a few games with many reduced-point units, and they've always gone just fine.
One thing I'd add from experience is that 24 points a player really seems to be the sweet spot with the Rampant series (odd, that, as it's the recommended size!). We went the other way for a long time, playing much bigger games. But when we cut back to 24 points each, the experience was much better. So I reckon single/reduced-model units is a better plan than fiddling with the points total.