Not to push you on "what you don't want" - but I had a remote gate, same issue. I used an ubiquti for wifi, installed a PoE hub for 3 cameras, ran it all off a 12V battery and solar. These days can get some pretty good USB based LED spotlight systems, even solar.. At 900', I'd definitely stick to 12V.
The ubiquti wireless system was better for us than 800' of CAT5/6. We had damage every 2-3 years from proximity lightening and ethernet. If you're going to do it wired, make sure you get shielded wire and ground it.
I kept it all in a I group 24 or 27 "battery box" and used outdoor rated CAT5e. You'd probably need a 2nd battery box. I was running with 100 watts or so of solar. My charge controller would shut everything down if battery got too low (which would take 3-5 days of no sun).
I like the idea of running minimal power out there, if you have to do it, just keep a basic "charge circuit"..