Defense used to mean jump in a plane or tank and hold attackers off.. not circle in ultra ack guns and run boxes of supplies into a town.
Who wants to pay 14.95 to do the later of those two?
You're asking the wrong question.
The question you should be asking is "What effect will the proposed change have on player behavior?"
I submit that the answer is not "It will make combat-shy players get in planes and fight in the air."
Whether they SHOULD be doing that is a very different question from whether they WILL do that. If they are determined not to fight you air-to-air, there's no way you can make them.
What nerfing M3 resup will do, especially late at night (which is what we're talking about here) is make it much easier for a small group of players to WF and deack multiple fields along the front, wait an hour or more for defenders to stop babysitting the map room, and come back and sneak them.
How about this for a change: reduce resupply effects on towns, but if there's no enemy plane or GV within range to flash a base or town all the buildings and guns lose 10% of their downtime per minute - meaning if no enemy ever showed up they'd all pop in 10 minutes regardless of strat damage. That won't hurt opposed attacks at all, because you'll always have some attackers at the scene of an opposed attack, but it will cut down on people sneaking bases unopposed when they deacked and WFd them 2 hours before. It won't even stop most sneaks... just the ones that depend on waiting for the defenders to get bored waiting for attackers who never show up for an hour or more.