I would also add that previous Lions tours and the RWC showed that experience counts. Barring injury there are certain players that are near certainty to be picked whoever the Lions coach is because as McGeechan calls them they are proven "test match animals". I would put the following in this category i.e. as long as they are fit in time they will be picked:
Hartley - maybe controversial, but last Lions tour proved you need a hooker who can throw under pressure and front, middle or back and his line out stats for England have been exceptional. Not to mention being a Kiwi he'll know the conditions well. He will also have something to prove after missing the last Lions squad and RWC through his own indiscipline. Plus there isn't a lot of strength in depth in this position imo.
AWJ
Sam Warburton
Sean O'Brien
Toby Faletau
Johnny Sexton
Jamie Roberts
Lee Halfpenny
George North
The rest of the squad; likely 37 based on 2013 Lions tour will obviously based on form from now on; both club and country, but a deciding factor will also be how well they played in previous Lions tours e.g. Lydiate isn't in great form at present, but if Gatland is Lions' coach I'm 95% certain he is another who will definitely make the final squad.
As Saint4805 says the ***le to this thread does say "early thoughts".