I agree, this tank's offensive abilities are among the worst in the game even when looking at tanks that are 2/3 the price.
Buffing the mg is probably the most effective solution. It's decent vs tanks but terrible vs infantry and if you adjust the AOE that can make it a squad wipe. Nice even MG damage is the safest way to make it effective but not annoying. The T34 was terrible until the hull mg was buffed and th KV1 has essentially the same offensive stats as that terrible t34.
That's because its T34 gun.
And yes, buffing its coax MGs to T34 level would be sufficient.
Its not meant to fight panthers and its durability allows it to be efficient vs P4s and even StuGs to a point, albeit it'll take a long time to win, it'll win.
I was always for buffing MGs before touching the gun for AI purposes as MGs allow for reliable DPS and are pretty safe from random squad wipes.