Not sure what his chances are, but I'd like to see Snake added back as DLC. As 'out of place' as he may be, there was a certain charm to him I kinda miss, and unlike other 'unfitting' characters like Bayonetta and Travis Touchdown, Snake is a gaming icon in his own right, so his inclusion doesn't bother me in that regard.
That, and I would
love see MGS and KI Uprising characters interact with each other during Palutena's Guidance on Snake.

Though I wonder, if Shadow Moses Island was brought back, what would be done with the codecs for SSB4's newcomers? Would they go without?