It doesn't really seem like Hall is being platooned, because there just aren't that many LH starters (it doesn't even feel like they PH for him that often).
In the old NL his bench job would probably be safe, though of course he also wouldn't have a DH job. Thomson said he expects it to be a tough transition for him to playing less (but that implies he sticks around).
At this point Harper might not be back before roster expansion anyway so they probably keep both Hall and Maton w/o ever optioning one of them. But I guess we'll see. Certainly Hall over Munoz or Camargo as the extra piece.
His presence does add a twist to the Hoskins debate, if it really is one. You definitely could get by with Hall as the LHB and a cheap RH slugger (in addition to the guys the Phillies already have) if he's for real, but also probably can't know that before next season.
One caveat on LGJ - he wasn't a true #1 pick. Obviously still a huge bust, and obviously lots of guys taken from 30 to 60 or 70 (he was 39) still work out, but I'm sure he's also someone they never would have taken at 1-20, maybe even not 25 (I guess had they had a real pick that year it would have been around there).