History has proven this cripples ukf against sniper play. Back in the UKF beta bolster DID come later, it was specifically brought forward because of the issues they had dealing with snipers: low model count, expensive individual troops, awful moving accuracy and no reliable counters.
Their own sniper now aiming faster than a vet 0 ost sniper recloaks helps a bit, but it has not addressed the underlying problems.
Iirc Tommies are actually cheaper a head than grens despite the higher squad cost
But currently the issu with delaying bolster is that Tommies are dog shit without it
Perhaps:
Tune the cover bonus so Tommies have the firepower of 5 man Tommies when in cover
Bolster removes the cover bonus
Output remains the same but durability increases as does mobility (not anchored to cover anymore) then bolster becomes more of a tactical choice than a no Brainer (or currently REQUIRED) upgrade.
The problem with a global dps/durability increase like bolster is its so bloody hard to balance, more so on units that are supposed to carry their faction. If it were me I'd be done with the global aspect of it and balance it as an individual upgrade.