I’ll second Dentalus, I don’t think that making that change will damage game play.
Actuality, I think it might be an improvement on the rules-as-written. I like in Dragon Rampant having 12 or 6 as the default unit size, in part because it makes reduced model units easier to manage compared to 10-5. 12 divides evenly by 6, 4, 3 and 2 versus 10 which only divides by 5 and 2. It’s possible to do reduced model units in XR, for example representing a unit of 10 with 2 figures that have 3 damage and a “leader” with 4 damage, but I find it way easier to just have 12 damage in the unit and split it 3 ways and not have to worry about who is who.