I think this has been suggested before, one strenghten the barracks. another suggestion, (which has been suggested before also) increase the number of barracks objects on the field and spread them around.
There probably could be 3x the number of barracks and have separate objects for supplies like a couple of warehouse building. Troops and Supplies separated. Also could consider the possibility of as barracks get destroyed then number of troops available are reduced by percentages. All Barracks up then 100% troops, you can load 10 troops. Barracks 50% down, you can only load 5. Barracks down to 25% you can only load 2-3 troops. Leave it like fuel is, 25% no less. You can still get troops just you need 4 or 5 M3s or C-47s for captures.