The Come is fine at it is, its basically a panther with less at and a bit better ai stock performance but when the panther gets it's MG the ai performance are pretty much the same.
The reason we don't see churchill's anymore is because of the pop cap nerf.
I think the commander upgrade give only a vision range buff and i'am not 100% sure but the xp gain was removed years ago and the accuracy buff is also so tiny that i makes no difference.
AI performance pretty much the same?
Have you ever used/fought a Comet before?
Even back when it was not very cost effective, it was still better against infantry than a Panther. Since then it got a cost decrease, mg buff, and a main gun buff vs infantry.
I like the concept of the Comet as a generalist battle tank with lots of utility. The armour is probably the problem, since it has a high chance of bouncing AT gun, shrecks, and even Panther shots. Stugs and JP4 aren't going to cut it either, although stugs still get used cos they're dirt cheap. 290 armour is basically heavy tank level armour, but it moves like a medium and has war speed.
It can get a slight cost decrease or minor buff in other areas to compensate if we nerf its armour, but 290 armour on a spammable speedy tank really should go now that the Comet is actually good vs infantry. Alternatively increasing its cost by 30mp and 10 fuel would put it closer to heavy tank costs, which is where its performance is approaching. For reference, the Comet handily defeats 2 x P4, and basically trades HP for speed, making it pretty much a Pershing with a worse main gun but more special abilities.