In my opinion, you are overthinking what you need. Since you have power available, my advice is to put up a couple of good PoE cameras and record the video on a PoE-enabled NVR. Install a router to create an "ad hoc" network at your property for the cameras and NVR to operate in. It won't have an Internet connection, and neither will it need one. The cameras will record to the NVR, which you can set up for motion detection only. When you visit your property, you will easily be able to review any of the video clips on the NVR without climbing ladders to remove SD cards.Anyone have any luck findng such a simple, common sense item for sale on the market anywhere?
This has numerous advantages. First, the video is not stored in the cameras, so destroying or stealing them won't cause you to lose your evidence. Second, you can hide the NVR so a thief won't easily spot it and steal it. Third, you can connect the NVR to a UPS to continue recording even if your property temporarily loses power. Fourth, a good surveillance-rated hard drive will last much longer, and be much more reliable than an SD card.
For a few hundred dollars you can have a system that will do everything you need. You can configure it and test it at home, then take it up to your property and install it there. The only drawback is that you won't have access to a network time server, so you'll need to remember to reset the NVR clock whenever you visit.
Also, with the right cameras and NVR you won't have to choose between continuous-time recordings and motion-detection clips. You can have both - the motion clips (or still shots) for quickly reviewing what happened, and continuous-time recordings in case you need a more complete record.