Like any army of new conscripts, there will be those who will run, those who would not know what to do, and those who'll keep a level head. I certainly understand what you meant, DA. As one author have said, war is a brutal Darwinian process.
John, I've read the Hyperwar too and it's a good source. There were certainly reinforcements being sent to the Philippines but these were diverted after the attack on Pearl Harbor and Clark. Now, if those reinforcements had arrived, it could've been put to good use. Southwest Pacific Vet who was in the diverted convoy, saw it differently, though. He was glad the convoy was diverted or he could've been trapped in Bataan, too. At least that's his sentiment on the matter.

Right now, I see the discussion revolving around numbers. I remember a lively discussion on the reinforcements issue in another thread.
Now on the offensive, I would say what the USAFFE could do is to conduct local offensives to restore the line. It's highly unlikely the garrison could push the Japanese back into the sea. Local offensives, however, cannot be sustained indefinitely so Mac's on the losing end in the long run.
DA, you kept pointing out that Mac should've stuck to the original plan. I see your point. If Mac had done so, he would've been in a better material shape. But I have to point out that the plan also included that he would be reinforced. That part of the plan was rescinded.
Allow me to take some historical liberties and alter the timeline a bit. It's what I think could make a general offensive feasible.
A. Mac follows the original plan AND his air force survives with very few losses in the first Japanese attacks.
B. With Mac successfully holding out, the Japanese MIGHT decide to refocus its attention in the Philippines and POSSIBLY suspends other offensives.
C. This relieves the pressure earlier for the Allies, forcing the higher commanders to reconsider sending reinforcements to the PI. Under the original plan, the US Navy would escort the reinforcements but the hit on Battleship Row "crippled" the Pacific Fleet. But since it's seen that the PI garrison is delivering good results, then it wouldn't be a case anymore of reinforcing defeat.
If that happens, Mac would've the fresh troops and supplies to strike back.
My scenario, admittedly, plays fast and loose with historical facts because it's the only way I can think of for conducting a sustained general offensive. Bottomline, at least for me, without those reinforcements and reconnection to a supply base, the PI garrison couldn't mount a general offensive.

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That's about it,
Fil