Infantry - Snares always engine crit
Light Vehicles - Puma reliably pens the M36
How does this not help Ost? A single Grenadier can prevent a Jackson from diving after wounded tanks.
As Hannibal said, the Puma is OKW-only, at least in terms of non-doc.
As for pen, like I said, this really wouldn't help. The M36 has enough HP that even a reductions to near-zero armor (just enough to protect against small arms and 222/Luchs), it really wouldn't change anything. The puma has pretty bad moving accuracy (0.5, like most vehicles), so it won't really be able to chase the M36.
Even then, if we assume a 100% hit rate combined with a 100% pen rate, it'll take the Puma six hits to destroy the M36, which will take around 23 seconds. Meanwhile the M36 can 2-shot the puma - meaning a single hit forces a retreat.
For the Infantry snares, this really only works when Axis is on the defensive, protecting against dives. When being offensive, this just won't do anything. When attacking, no (good) USF player would let your grens get within 30 range of their M36s, either by simply moving the M36 away (it's really fast), or by focus firing the closing
4 model squad with their double-upgraded/vetted rifles. Additionally, by default, when you're closing in on those M36s, you're also closing in on rifles (since they're almost certainly screening for the M36s), which means you're setting up a Gren vs. Rifles at meedium/close fight; that won't go well.
What about making jackson sight dependent on movement?
I mean, its like a passive spottig scopes, but current sight is only when stationary and on the move is half of it, for example.
Jackson will no longer chase reliably, but can defend
While it could work, I think this is just too gimmicky. Not only would it be really frustrating to play with (depending on the severity of the moving penalty), it's just another "we want to nerf the M36 but not really" change.
A similar comparison would be the JP4; for some reason it has a vision 'cone' rather than circle; meaning it can only see in a ~90-degree cone in front of itself, rather than in a full 360 circle. This seems like it would be a pretty big mechanical difference to have, but many players don't even notice it, because other units are giving LOS to the sides/rear of the tank. I only noticed this 'cone' late last year, despite playing OKW since release (or shortly after).