IS are very good infantry straight out of the gate, and become /extremely/ good even just with Bolster. You don't need bolster and double brens for them to be "halfway decent"
The 17 pounder (like all Emplacements) is not great, and decent players will be able to deal with them pretty cost effectively.
The firefly is... Ok, though the SU-85 and Jackson especially are leagues ahead of it.
Brenmandos are very strong, though very expensive... Though SOV not having optimal INF DPS really doesn't matter. That isnt really what their infantry are for.
The Comet isnt the same sort of tank as the Panther. What sort of weird strawman is the idea that you need "15 AT guns and 5 TDs", anyway?
Weren't you complaining about the Vickers not being very good earlier on?
The reason not to play UKF is because they are a fundamentally flawed faction, even if they "fit your playstyle".
my two cents:
infantry sections feel weak for their cost, but become terminators, once you give them the command vehicle aura and brens, even outside of cover
The 17 pounder is a situational weapon, it seems to be best used for elefant deterrence
The firefly pens, hits, and has tulip rockets,
and the vickers hmg is unreliable, but its, like every other MG in the game, better than the maxim