Guards are effective vs infantry, because if they weren't, the squad would be utter trash.
Call-in squad armed with AT weapon that does not perform well unless spammed and is completely useless vs heavy armor should be effective vs infantry.
Why would you get that squad otherwise instead of teching to PIATs and equipping REs with them, creating much more potent and scaling squad?
AV tommies should have their AT snare at same range as other snaring squads.
Because unlike double PIAT Royal Engineers they cost no munitions, they have a snare and they come out at a much earlier window. Personally I'd leave them be but if they have to change I'd rather see AI power shifted to AT than see them become yet another special case exception.
If they not an Infantry Section they shouldn't have the Infantry Section's name, icon and portrait. If they are an Infantry Section they should be affected by Bolster and be able to take the upgrades their icon leaves a big empty space for.