Anyone here that can/want to try it and debunk is welcome since i wont be able try myself for the whole week.
To 3) The assumption is incorrect. There is no veterancy offset. A vehicle crew of a vet 3 Sherman abandoning that tank and then entering another Sherman will make the sherman vet 3. Different vehicles have however different veterancy requirements - the amount of veterancy that needs to be accumulated. A Jackson, for example, requires 8640 experience points to reach vet 3, a Sherman requires 8080. So, if your Sherman just reached vet 3 and you transfer the crew to the Jackson, you'll end up with a vet 2 Jackson. Crews are able to accumulate vet even above the requirements of their current vehicle and if the crew has gained enough experience points within the Sherman they can also turn the Jackson into a vet 3 Jackson.
Vehicle crews also vet up a lot faster, in terms of the veterancy level displayed (as stars), than their vehicle. A vet 3 vehicle crew is no indication of what the veterancy level will be of the entered tank as the crew reaches vet 3 after 2600 experience points and just keeps accumulating experience after that.
To 2) Making the crews more vulnerable is problematic since you'd nerf for example armour company's Thompson upgrade on tank crews and basically make vehicle crews not viable as infantry units, which they are not already but at least they can be used as such in certain situations. You also make the m20 crew with the zook more vulnerable and thereby make them worse as an early soft counter to light vehicles.
I would propose a different approach. I am not sure if this is possible with the mod tools:
1) Remove abandon as it is now as a mechanic. If the crew is told to jump out spawn a vehicle crew with the veterancy of the tank and completely disable the tank (similar to how Soviet vehicle crew repair training disables the tank). This way the constant discussion around pop cap abuse finally seizes. The popcap of vehicle crews would have to be lowered. With this the tank still fully adds to the pop cap. The tank is re-enabled when either the crew or another usf unit enters it.
2) Have crews automatically abandon and have a 50% chance for each model to survive, similar to how it works for clown cars and units inside them. No automatic retreat, the player should have to react in order to save their crew and there has to be some risk. This is in my opinion a better approach than to lower the survivability of crews and thereby nerf a lot of other applications as mentioned above.
3) Send home option: With crews abandoning tanks and the chance to survive, you'll inevitably end up with a crew that you do not need or do not want. The option gives you the possibility to send the crew "home" when in base and gain a 100 mp refund (or something more appropriate).
(Optional) 4) "Fix" radio net: