only that it isn't. both ost and brit sniper get oneshot by each other. even if it was legit asymmetrical balance, you are still cherrypicking here, because, like i mentioned above, there are multiple other instances where allied units are quite clearly and obviously stronger despite exact same role and similar costs. again, you only use the argument when it fits your narrative and not in general.
Ost sniper has a higher fire rate, therefore it is more effectvie vs infantry. Also, where do you see these "quite clearly stronger allied units"?
It does serve its purpose, because it IS countering light vehicles, it just cannot take on medium tanks on its own (and again, if it could, it would be OP, even by your definition). it very well can take on medium tanks if you have two or three of them, negating the argument that the unlock costs can be added to the price.
Refer to the 600 MP Obers that serve their purpose too. Making 2 or 3 AECs does not make sense by your own definition, you'll just be better off with a cromwell, because its single advantage over a cromwell is its arrival time.
And i want rifle vet for grens... and 5 man squad upgrades, bars instead of lmg42s, a sniper that can counter light vehicles, emplacements that have a "can't kill me" button, forward retreat points with weapon racks and reinforcing, having to spend only 30 muni once to be able to heal all my squads all the time, cloakable infantry that is deployable everywhere on the map with insane dps, tanks that can survive roundabout 20 pak shots and throw grenades, indestructable artillery pieces in my base and so on and so forth.
Rifles have stronger vet and combat effectiveness, grens are cheaper, and they get literally everything for free (lmg42, nades, faust). Why'd you want bars instead of lmg42 is beyond me since the lmg is clearly better. Ost doesn't need 5 man upgrades because their mainline infantry is cost-effective without them, emplacements with brace on have as much EHP as an okw truck, idk why you have trouble killing it, its so easy for allies after all
. FRP with reinforce costs 450 manpower, I'd really love if that was also a tech structure... I also can't understand why you consider weapon racks as an upside, opposing to upgrading on the field. Commandos cost 500 MP, churchills can throw nade at about penal satchel range and have a bad gun, and don't get me started on the all-powerful 25pounders that cost 45 muni to fire and won't kill a bunker off of that.
The only thing that could be arguably strictly better is tommies' self-healing, but it is negated by the fact that it's the only source of healing, leading to awkward situations where the only tommy is on the other side of the map and you have 3 unhealed squads sitting in the base.