Robert really would have needed Lyanna, she would have whipped him into shape. ;) Renly's beard situation seemed to work fine, although I wonder how long Margaery would have been happy with that. I know, there are some theories that she's lesbian and banging her cousins, but if she isn't and actually likes guys, she might at some point hate having a handsome, gay husband and not being allowed to have a lover herself without causing a scandal. And Stannis ... I really can't think of many canon characters that would have made a good match for Stannis (other than Sansa ^^). Catelyn might have worked, I suppose. But Selyse was just a horrible choice.