All are great ideas. The budget will cover equipment that will be used in future shoots as well - which in that case future shoots would be more $ in the pocket.
I would probably settle on the FS100. Maybe 2 of them. The look you get from that is extremely pleasing and in some cases look just like they came out of a RED camera. The biggest plus I see to a RED camera would be the HDRx processing which is very appealing, but at what cost? 4k video streams would be overkill for the general use of these videos, but I could see it being used for the occasional pan and zoom without losing quality in a 1080p output.
Lastly using these cameras out in the field, I would feel a whole heck of a lot worse if I dropped a RED camera rather than a FS100!
You could get a FS100, with all current (or soon to be released) E mount lenses, a matte box/rail system, and plenty of 32GB SD cards for under $9000. I already have about 15 NP-F970 batteries that my Z5s and lights use - so I don't need much of a budget there.
I do have a question though about backup devices. The ATOMOS Ninja 2.0 recorder looks like a great idea and have heard great raves on these forums about it - BUT - I use a PC and Vegas and are the "pro res" files it captures compatible? Any other recommendations for instant backup?
Thanks all for the info so far!