I noticed today that you can send marine reinforcements to allied vessels to help them defend against capture and hit-and-run raids! The "max marines" limit is not enforced in the tactical mode. Only spacedock limits the marine loadout...so you can redistribute your fleet's marines however you choose once you enter battle with some coordinated beaming. This would most likely be used to beef up the defenses of a ship like the KVL which has a completely insufficient complement of marines for its size. Warning: you can also hit-and-run friendlies if you're not careful with this script.