I'd welcome Southgate back. I think a few years tutelage under Ged would be ideal for him.
I don't think he did too bad a job at Middlesboro, if anything he just had bad timing, joining just after the big spending days. I'd also suggest his record stands up against Strachan's (...who's record at Celtic was comparable with...).
He clearly has the ambition and wants to get to the top. With Ged providing contacts etc it could work nicely.
I'd throw Grayson and Cowan's names in there too.