For what it's worth, assuming Gats takes 37 players, as he did in 2013, my Lions Touring Party:
Back three (7): Hogg, Zebo, Watson, Williams, Daly, Nowell, North,
Centres (4): Ringrose, Henshaw, Joseph, Farrell
Fly halves (2): Sexton, Biggar
Scrum halves (3): Murray, Webb, Laidlaw
Props (6): Marler, Vunipola M, McGrath, Furlong, Cole, Sinkler
Hookers (3): Best, Owens, Taylor
Locks (5): Launchbury, Wyn-Jones, Itoje, Gray J, Lawes
Back row (7): Stander, Warburton, Vunipola B, Faletau, O'Mahoney, Haskell, O'Brien
I suspect Gats will take Halfpenny for Zebo, Seymour for Nowell, Davies for Ringrose, Youngs for Laidlaw, Hartley for Taylor and Kruis for one of the back row, as Itoje can cover there. Except for maybe Kruis, I wouldn't have any of them anywhere near a Lions tour. Tough on Tiperic, Finn Russell and Jamie George.
Have at it!