In regards to pulling off fiber as the run goes, yes that is possible, a pain dealing with the armored cable but is done by many people. A fusion splicer would also not be needed, a box like this (for example only, not promoting this style or company, there are a few to pick from):
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwiS9LOT-uXJAhVE7yYKHRN-AcsQjRwIBw&url=http%3A%2F%2Fwww.alemsan.com%2FFiber_Optic.html&psig=AFQjCNE5W0wIUu0y8otnYvnJi2Qt3XYOBg&ust=1450546809899736
Would allow you to "peel off" a strand or two. Then you would just need to put an end on the fiber, which you can do with pre-made ends that have the gel and everything you would need built in, you strip the fiber back exposing the "glass" then insert that into the premade jack and snap it together. This would give you the end to plug into the above box on the inside. You would then need to purchase a fiber patch to plug into either the cameras or into a media converter to convert it to copper.
For example (5 strands shown below) the first strand is terminated early in the run, the second strand a little further down, and the others keep going until terminated even further or kept as spare:
-------------------MDF Splice Tray--fiber patch--camera/converter
----------------------------------MDF Splice Tray--fiber patch--camera/converter
------------------------------------------------------------------------------->
------------------------------------------------------------------------------->
------------------------------------------------------------------------------->
You would not need to cut each strand every time you need a camera along the run, that would put to many splices on the last strand (to many being an arbitrary number, depends on quality of splices, distances, etc), presumably you would have 11 splices for the 12 strand before it got to its ends device.