Don't quote me on this, because it may not be 100% accurate, but as I understand it...
As long as there are "Similar" numbers on each side, then it's not considered milkrunning. Because strats are not working correctly on this map, fields are fair game as long as there is sufficient numbers.
I wouldn't go dropping in hordes of troops. But I see no reason why you can't attack a field, de-ack it, blow up structures, and even attack the planes defending. Just make sure it's not a 5 vs 1 type deal.
If the Axis have 5 players, and the allies have 5 players, and the allied pilots are organized and working togeather. And just 1 axis pilot is defending the base you chose, and those other 4 are just off someplace else (probably attacking an undefended base as well) then I see no reason why that isn't legitamate.
The italy map is SOOOOooooo much larger, that I don't see it having the same issues that the earlier two rounds propagated.