My suggestions would be:
IS cost down to 260, bolster now per squad upgrade taking 1 weapon slots.
Available option:
1 medic entity that give the heal option
1 entity with a scoped enfield gives the pyro upgrade now has a timed ability similar to pathfinder critical shots, take all weapon slots.
1 entity
As mentioned before, I do favor similar changes (see my response to maahowl, for instance). However, I stand by my previous statement: "the Bolster to T3 is probably the simplest change."
Vickers simply get a timed ability similar to maxim they are both water cooled weapon anyway. Some adjument to damage might be needed.
This would also be an interesting option, perhaps similar to the Maxim's (unlocked at Vet 1).
The AOE profile will need allot of adjustment since it was designed for 80 damage. (it already needs).
Imo the unit should be redesigned as an infatry support tank with less penetration and damage output (currently has the same penetration as AEC) but higher durability. Armor could go up and also have the ability to fire smoke rounds.
I looked at the AOE profile of the gun previously, and it is nearly identical to the Churchill Mk. VII's. Thus, we have a clear benchmark of its anti-infantry performance, which should be adequate.
Bofors already gets sight with veterancy.
Emplacement simply need a redesign that includes bleed and some sort crew or interaction.
For instance their performance is lower if they do not have garrison, the get a ability to auto-repair costing manpower or munition and so on.
I'm in favor of emplacement redesigns that turns them into units you actually need to invest micro in. However, as with the Bolster change, I'm going for simple changes.
The valentine can be simply replaced by a artillery commander upgrade providing the abilities of valentine currently has to any vehicle above UC.
Valentine abilities would be Sexton Concentration barrage, which is practically useless unless you have Sextons. Combining the ability with the regular Concentration barrage (that already exists in the commander) would probably be the easiest solution to keep its usefullness in team games.
Additionally, a decent indirect fire unit in an indirect-focused commander is not only thematic, but as Stormjager said, "fits UKF like a glove".