As far as the Dragoons--they won't be on New Avalon.....
Unless I read Divided We Fall wrong, sooner or later the entire organization will be with the Wolves on Terra, fighting the Jade Falcons.
That means the Ryuken, Sword of Light, and 2nd Genyosha are the only Combine mech forces on planet. While the Sword of Light and Ryuken are rated as elite, both are at 65% strength as of 3145. The 2nd Genyosha are Veteran rated and at 75% strength. I would guess during the occupation of New Avalon all of them are similarly understrength in 3151.
So you have a very high quality of occupying forces, about 6 battalions of mechs total, with supporting forces to boot. Somehow, I'm feeling optimistic that 3151 will be a very poor year for those Kuritan forces on New Avalon.