What makes people bombarding it? lack of soft counter. Don't you think people try to destroy it to cutoff your production or because a rally point that heal and reinforce in the middle of the map is a pain in the ass to deal with? 
If I see the okw-player retreats units, I try to let my mortar finish them off. Simple.
It´s a "pain in the..." and so you want an easy way to take the pain away?
If I have the opportunity to disable its abilities, faster than destroying it, I'll disable its abilities and many people will do the same. And you it gives you more time to take back the territory and get it before its destruction.
If the truck isn't used aggressively you'll not face this situation. Does OKW only need to use it aggressively to win a match. No.
Does it forbid OKW to play aggressively to win a match, no, but it gives more gameplay around it.
It would give allies further earlygameadvantage and okw would have an even higher risk, resulting in more and more defensive playstyles and okw is not meant to play defensive...
Now think I'm only talking about gameplay, not balance - so of course if those mechanisms have to come live, a balance design would be necessary to make sure the faction doesn't become rubbish because of it.
You want to tweak corefunctions of the faction that is a "pain in the ..." for you to deal with.
This mechanic is not only about gameplay, it directly affects balance.
Just try playing okw for a few games and see things from the other side of the table.