Way to narrow your thinking. Stuart would be fine with 400 health and T-70 could use a minor cost decrease, but let us not forget the Recon Mode and Self Repair.
Show me a single situation where self repair made any difference.
Year ago it could repair single faust damage, now its useless waste of ammo.
Both stuart and T-70 could get same survivability treatment Luchs got.
There is no reason why Luchs would be more durable then any of the two, it had LEAST armor and worst armament out of the three, yet here its cheapest and most efficient in its role.
I'm not saying it should be nerfed(before angry fanboys aka Jaigen will jump on me), I'm saying other two should be on its effectiveness and survivability levels-no reason why they should be below.