: Where's the battalions of soldiers armed with captured Covenant weaponry?
: Where are the ODST suits enhanced with materials acquired by cutting
: Covenant armor apart? Where's the negotiations with the Covenant Fringe
: for obsolete starships?

It's been mentioned many times in the novels (and borne out by the games) that the UNSC doesn't know how the Covenant recharge their plasma weapons. You'd have battalions of soldiers armed with plasma rifles and plasma pistols and so on with single-use munitions that would have to be discarded and then newer ones obtained.

Also, the gunnery sergeant on Cairo Station mentioned that the Chief's shields are more resilient than the old Mk Vs was, stating it was "much better than the Covenant tech" it had been adapted from.

I'm not saying whether one method or another is better, just pointing out some instances where the fiction has given some answers to how some of it works out.