So I was playing MCC (Blargh) Halo 3 (Yay) Single Player mission the Ark, and the ODSTs you start with, Ive discovered a way to keep them at least up until you enter the wall and get separated (Assuming you actually protect them and manage to keep them alive up till this point.
So after we rally up with the crashed pelician, you should have 3 ODSTs (White Shoulders) and a ODST Squad Leader (Red Shoulder Armor), I usually arm them each with a Carbine, and one with the Battle Rifle at that point. At the crashed pelican you meet up with two standard Marines, toss them the Sniper Rifle (The one with the assault rifle) and then jump straight down towards the pelican to grab rocket. launch one rocket at the covie group heading upward where your UNSC ODST and Marine forces are hiding, hopefully taking out the brute, at some point some brutes will step out from behind a rock up there, use BR on them, and finish off Grunts. This part is key DESTROY the ATVs and KEEP the enemy Brute Prowlers alive, this will give you one fully loaded (With you driving) and one almost fully loaded (Missing one Marine) Prowler convoy. If you are doing this in co-op then even better. Anyway, Becareful clearing out the next few areas up untill the Forward Unto Dawn swoops in, try not to flip the prowlers scattering marines everywhere. Anyway, when they get out, the ODSTs will make a break for the nearby pelican after giving you a salute. Run after them and swap weapons rapidly with them, This will cause there AI to “Pause” to swap weapons consistently allowing the “scene” to finish playing out, johnson’s dialog, the unloading of the Scorpians and etc, when Johnson is done running his mouth with Keys, the Pelician will start to take off. Give the ODSTs there weapons back and resume gameplay as before, but now you have 4 additional troops to help fill the vehicles up. Those ODSTs alone can give some nice additional firepower to a single scorpion alone so its a nice reason to keep them around…