If you wanted to continue as a rogue, anyways, I don't see how a 3/4 BAB and good Reflex save (including an additional +2 boost at 1st level) can hurt there!?
If you end up as a Ftr4/Rog12/SToA4 you'll actually gain a net +2 Reflex save and lose no BAB at all. You will lose two rogue special abilities, however, which are compensated by two bonus feats along with the +2 Reflex save and some other minor stuff.
You could also go Ftr4/Rog13/SToA3, which will still net you +1 Reflex save, but -1 BAB, only one rogue special ability less than the Rog16, which is nicely compensated by an additional +1d6 sneak attack and a bonus feat plus the minor stuff. The loss of BAB means one attack less at 20th level, of course. Not a really big penalty, tho, the 4th iterative attack is pretty weak at -15, anyways.
Bye
Thanee