Agree that all three would be great additions to the squad at the moment. Even Hibbert, it could allow us to push Seamus up if necessary and although we are all (himself included and most especially, I imagine) enjoying him at right-back, given the dearth of right mid options he'd be a welcome boost. That would pale in comparison to a fully fit Mirallas who would allow Seamus to stay at rightback and give us a whole new depth in attacking play - although we drew 2-2 Fulham away, the Jelavic/Osman/Pienaar/Mirallas combination with Baines and Coleman bombing on was a joy to watch, we were absolutely incredible going forward that day. Having them reunited & with Gibson would give us real hope in that battle for 4th.
I think Gibson will probably miss Southampton; I have heard nothing on Hibbert - but there are whispers Mirallas will be back for Southampton. I imagine he will start on the bench even if fully fit and will get no more than 20 minutes. Here's hoping I am wrong and he's fully fit and in the starting lineup