The only thing I agree on here (except if I misunderstood a bunch of what you said) is:
- Improvised Armour: should add improvised armour pieces to the vehicles. (skins go against the grain in that sadly, but gameplay takes precedence over cosmetics, of course)
- DaK has too many HP upgrades to make visual changes practical perhaps, but it could be done:
> Smoke & armour upgrade: at least smoke canisters modules poping up.
> Self repair & health upgrade: Side Skirts on Tanks, bunch of accessories & tracks add-ons on halftracks?

The less icons the better, visual changes have to be read on the vehicles. There's already near-too much icons floating around taking loads of space as is it.

I agree with Haganaz. Spamming too many distinctions would also be bad and would make more work for the team, that they can otherwise spend doing much more important stuff.

For universal upgrades a visual distinction doesn't even make all that much sense since you see it used once or notice the health diff once and you know every unit has that upgrade.

Visual distinctions make sense for specific unit upgrades. For example sprint on rifles. It would be good to know if they have it or not because you would then know which rifles you need to be more careful around. Most specific unit upgrades have some sort of distinction so it isn't too bad in that regard though.

so the better idea is to combine the ability with veteran, you will know what you are dealing with by veteran, it is more clear.