Agreed! unrealistic bull m3 rebuilding towns in min, faster than you can bomb; M3 is not a cement mixer, was not designed to haul building materials and rebuild cities; concrete needs 2 days to solidify and takes weeks/months to fight the bureaucracy for a building permit.
This aspect of the game is not meant to be realistic. If we wanted it to be realistic, carpet bombing towns should make them
harder to take, not easier - IRL, rubble proved easier to defend than buildings (See Stalingrad, Monte Cassino, and Caen).
What this really represents is bringing in extra defending troops, but it's abstracted so the game doesn't get bogged down in massive land battles with AI infantry slugging it out. There's no need to turn AH into another 1st person shooter and even less need to make the game depend on massive infantry battles in which human players can't directly participate, so instead we have an abstract mechanism for capturing bases on the ground once the defenses have been softened up from the air.
Attackers have a number of options to keep the town from being be resupplied. Take out troops at the base or bases that spawn in, knock down the city and/or ack strats so it takes a dozen loads of supplies to bring the town up instead of three, have troops spawn in as soon as the attack commences so they're there to make the capture before enemy M3s can drive in from their spawn, or best and easiest of all, have the fighters who deacked the town stick around to kill incoming M3s. M3s are completely helpless against even a marginally competent pilot in a fighter, and if the defenders spawn wirbels that's extra players who aren't resupping the town or defending in the air - and also combat, for those who say that the resupply mechanic takes away from combat in the game.
The downside of making this change that no one has mentioned yet is that it would mean attackers could take down the city strat then fly around bombing a dozen different towns all of which would be vulnerable to a sneak attack for the next two hours. Nobody wants to have half the country baby-sitting white-flagged towns for hours on end waiting for attackers who never come, but that without the option to resupply that would be the only way to defend airfields from sneak attacks. Sneaking bases is a valid tactic but there's no reason to make it much easier than it is now.
This is a well-balanced aspect of the game that doesn't need to be changed.