@kdfrawg I just looked into it again. Crashplan either changed their policies or I had them confused with another service (probably Backblaze). Though they don't support running headless on a NAS, they do actually document how to set it up so it'll probably work.
For $150/year, I probably should suck it up and give them a whirl.
Thanks! :)
/@hazardwarning @jmreekes