The other thing you mentioned is the complete block of OKW out of base buildings. Every static HQ is wiped after air superiority which is a big kick in the nuts for the OKW player from which he often cannot return. OKW HQs are meant to be placed outside the base. Yes it's risky but it's a fundamental part of their gameplay. This shouldn't be countered by only one ability.
An OKW should perhaps be more aggressive in taking the munitions to deny them the ability.
Also, the truck costs less than the ability...
Self Destruct should refund ~75% of the building resources or a flat number (150 / 30?), and call the next truck in instantly if a replacement isn't already on the field. That way you can counter-play bombing runs at a cost to yourself, but not completely nullify it's worth because you're still taking a hit.
That would be overpowerered, making dislodging OKW as any other faction impossible.