As always, you make some excellent points, and I won't say that I had thought my way through all of them before deciding to make some changes. Eventually, though, I stumbled into the light, or as close as I am ever likely to get. Yes, I could have ponied up the money for a commercially available safety thimble of one design or another, but I'm kind of cheap and I figured that I might be able to come up with a design that I could put together myself and save some simoleans.
I'll address your points in order, if I may.
The Warn thimble design was the main reason I went with the poly wheel as the factory hook/thimble combo was obviously capable of doing just what you described. Before I came up with the wheel idea I put a shackle on the bumper and attached the hook to that as a stowage option, but I didn't like it much because of the possibility of running the thimble into the fairlead during a winching evolution. The wheel acts as a bumper and helps to keep the line snug without putting it under too much tension while stowed. It is a moderately soft composition that has some give to it so as to avoid damage to the fairlead. I drilled out the inside of the hole just enough to get the line through it, so there is no part of the thimble that comes into contact with the fairlead. There is no metal to metal contact. I actually had to unreel all of the line to get the wheel on in the first place and it is nice and snug on the line.
As for the "abrasion guard", I never installed it at all, due to your (and lots of other folks') advice in previous posts.
Finally, I have, over many years of observing others, evolved a technique for handling winch line (or any other rope, line, hawser, sheet, stay or cable). It can be boiled down to one idea: Never have any body part inside a loop (bight) in any line or attachment thereto. It is easy enough to maintain a little tension on a winch line by grasping the thimble, shackle or hook by its sides instead of sticking a finger or two through it. and yes, I did test my new setup to make sure the system works as advertised. It does.