Stafford, those are the right things to think about!! And over MANY years, I have worked on answers and solutions. First, YES, you can anchor a boat/raft and leave it, as long as you are able to return to it, you can observe it, it is propetly licensed (if it has a motor), or if it is within 100 feet of a shorline if it does not have a motor. In the past, I anchored the raft 85 ft south of my island when launching kite (and by the way, the 'anchor' is one of those concrete parking lot bumpers) with a steel cable. Since I own the island AND licensed a 'Rocks' bouy off my island with city and DNR, that works perfectly (just a hastle to maintain the past 12 years...). That anchor solution with my raft even works with 17M kite launch by the way when overpowered...!
But with a motor (powerful nough to move raft upwind in strong winds...) things change a bit. First, one can leave a boat unattended and anchored as long as you are actively able to return to it; AND it is clearly visible. Thus I have a flag on the raft (as I have done previously with my pontoon boat) and I keep an eye on the boat/raft and make it a point to 'check in' with the police boat when it seems to indicate interest in my anchored boat/raft).
Unlike the swamp, my back yard has some very deep areas, over 65 ft deep. Thus, while I try to anchor (3 anchors on raft now with motor...) in about 10 ft water (30 ft anchor lines), I have to be prepared that rogue wind could move the raft, so some forethought about where it 'might' go is in the equasion. When in doubt, I play it safe... But in any event, with kite or wing, I know my lake, I get to know the right people (police, Lake District, etc..) and watch the weather closely.
Bottom line now is that almost any wind direction in back yard will work, but if we get east I like the waves on big pond!!