Winchers do work, but they certainly aren't as good as proper self tailers. OYOH, while they aren't cheap for what they are, they aren't in the same league as swapping your existing winches for the real thing.
I have 'em on Jissel, and if they died (they seem pretty indestructible) I'd replace 'em. Some people seem to get on with then, others don't. I don't know if it's a function of the winch size and loading or the user developing the knack or not.
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Simple answer - "sure" - it all depends on how pretty you want it ...
The best place to start is the US Patent Office - there are several add-on designs there. The simplest is a roller which presses against the coil on the winch drum so preventing slip.
There were also several self-tailing 'kits' on offer before Lewmar et al firmed-up their current designs.
This is a subject worth researching - lots of good viable ideas out there, just as long as you don't want 'pretty'.