Tommies cover bonus can be salvaged and it is not the cause of problem, it work for ostruppen for instance.
The rout of problem lies more to all the nobrainer upgrade tommies have available to them like bolster/medic/pyro weapon upgrades.
UKF would become allot more easier to balance if this buffes become side-grades instead of upgrade.
For instance:
Bolster becomes a individual upgrade taking up a weapons while tommies have cost reduce to 260
Pyro becomes an upgrade giving scope Enfields and taking up all slot while removing cover mechanism
Medic upgrade replace one entity with medic armed with a pistol
and so on
It would have been nice if there was something like 'recon' upgrade, giving them more accurate riles, lower range AT nades and slightly increased sight (with vet, perhaps in line what engineers have) + abilities from pyro. 4 men squad, upgrade takes 1 weapon slot.
Medic upgrade gives IS 5th men.
Remove bolster upgrade, but increase t1 price. Sappers always spawn as 5-men in this case. Remove sight bonus in cover.