A Rapeshaw can still help hold off a Mammoth rush, just not as effectively. I honestly didn't know the damage had been nerfed, though I saw that the RoF had decreased. 2 stanks can kill one fairly effectively as well. I was on Goldrush for a match with myself in a stank, and another team member in a stank. We held off the constant GDI attacks for some time. Between the 2 of us, we had teamed up to kill 4 Mammoths, 3 mediums, 3 APCs and someone who decided to run in with a Hummvee. There was a point where they tried a 2 Mammoth, 1 APC and 2 medium rush. We stopped the 2 Mammoths before they reached the entrance of our base. The APC was half health by the time it reached us. We took out the APC, and I ran over a couple engineers while I locked on and shot the mediums.
For the airstrike talks, why not make it something that is less expensive/easier to obtain for the losing side? It would help make it less overwhelming for a defending force, and make it more of a break the line tool for them as well. I'm not completely sure how you would go about determining the side that needs it though. I've seen matches where the side that held the enemy base entrance still lost from score. However, that is usually due to GDI base being empty and free for SBH to roam and take down buildings. It wouldn't be ideal to go just by score for maps that stay back and forth either, where neither side really dominates totally. So, again, I'm not sure how you would determine who "deserves" the airstrike advantage.