Hooking to the top of the cage sounds real scary to me. Red. It would be a lot of strain on the rigging up there, and if something let loose your prop and probably a lot more stuff would be history in the blink of an eye.
I like the idea of towing from the bow eye.
Here's something I've thought about ...... tell me why it wouldn't work.
Make a rope loop from some very heavy rope. Heavy enough to practically fill the drain holes in your transom.
If you wanted to tow somebody and you knew it was going to be a hard pull, beach your boat, pull your transom plugs, feed this rope loop through it, and go back for them ...... with your bilge pump running of course.
If the rope loop was heavy enough you wouldn't take on water very fast, and there wouldn't be any strain anywhere but down low on your hull.
What am I missing ?