I have a couple of those 'hook on the gate' type hayracks for outside and I made wooden lids for them, just 'hinged' by drilling three or four holes along the back edge and putting fencing wire through. Yeah, it rains far too much here to have hayracks outside without lids.
Even so, I think making some divides inside your shed, so they can each eat and sleep peacefully, is a good idea
Here Ellie used to attack Rowan. I penned them side by side, with a (very strong) wire mesh panel between them. They had some humdingers of head-butting fights through the mesh partition! But it survived, they calmed down and now Rowan has accepted her underdog status, they choose to sleep peacefully near each other and Ellie actually starts calling if she can't see Rowan.