Interesting mod. Good thinking!
I did indeed read about the first version of the Slide straps sometimes coming loose, however the newer versions have an improved design of the cords on the connectors that would prevent this from happening, or so they say at least... I believe the internals of the cords are now bright red, which should act as a clear warning sign when they would start wearing off, and when it's time to replace them...
I've had my K-3II on this strap (albeit a simple black one) for some time, and so far it held up very well. No wear whatsoever.
When changing straps in the field the human factor enters the picture as you state, and here your solution is a great one indeed. I've dropped my share of gear while quickly moving it about under pressure (my wife's inpatience mostly

).
@Kayaker-J: Which strap is best depends I guess. I'm sure the slim version will work just as fine, the "weakest link" being the connectors (=the same with both straps). I personally prefer a wide strap for better weight distribution, hence my using this size. I would even prefer it slightly wider still (my previous strap was a LowePro Voyager C, now discontinued). Of course a wider strap is more cumbersome to stow, so if that's an issue and you don't mind a narrower strap, the slim version may be better for you?
hth, Wim