Recon drone being allowed in spawn area would solve about 50% of this. Instead of a common sense solution like this, "They're a bit less accurate at max range". Oh, "It takes 30 seconds to resupply the mortar."
First, the accuracy has nothing to do with the problem of the mortar. The pressure it places upon players attempting to hold the point is the problem, even if it isn't landing hits. The resupply is silly, I have made the point here before that it takes less time to redeploy to get a fresh mortar than it does to resupply it, so guess what I do every time I need a new mortar? And since I'm going to plop that thing down in my spawn anways... no real loss.
Another solution would be to not start the player with the mortar. I would say this is a stupid solution, but if no other changes were made it would still be a better solution than nothing. Other than that, DRAMATICALLY lower the firing rate, and return the accuracy. Increase the rate you can get smokes too, I have no idea why those take 10 years to resupply, AND why you don't start with smoke rounds.