This is getting way too many
CPs for what it's doing. You're looking for a Patrol detachment (but more so) but giving it Battalion detachment
CPs... I really do think that you're underselling the ability for a series of Patrol detachments to do what you want. 1
HQ (warboss/synapse creature/etc) per 3 squads of goons. If you're looking for walls of bodies presumably each squad is max-sized.
But, going with what you're talking about. This should have
less command and control than even a Patrol. Another way to look at what you're trying to do is a Patrol with multiple Auxiliary detachments of troops, each of which would be worth -1
CP. You have to give up something to gain the things you want because anything else is the definition of "over powered."
I'd also name it something other than "Reinforcements." I was looking for the rules to keep it in reserves. Maybe a Phalanx detachment instead? Doesn't fit with the horde/mob concept you want, but fits with the military description used with the other detachments and doesn't sound like something that should be in reserve.
Phalanx detachment
HQ: 1-3
Troops: 4-12
Dedicated Transports: Up to 1 for each other choice
Restrictions: All units must be from the same faction. Each unit must have the maximum number of models allowed.
Command Benefits: -1 Command Point.
Tangential ideas this inspired...