Separating them during the day is not possible since there is only one run in shed for them to escape the dive-bombers. Hence my question.
You say you can't separate during the day, what are their arrangements at night? If stalled, just feed the guy that needs the higher quality hay only at night and leave them to have a round bale during the day.
Perhaps your guy that needs the higher quality hay would do well with a grain meal or 2 or some other forms of supplementation, i.e. corn oil, rice bran, etc.
Sometimes you have to burn a few bridges to keep the crazies from following you!