Hi Gary.
Since you've already got the brass & dies, you could neck all that .243Win brass down to .22-243Win.
All you'd need is a .243Win Redding Type S FL bushing die (if you don't already have one), and a couple bushings. Figure .250-.252" should cover ya, depending on chamber neck dia. & brass type. And you can use your standard .243Win seater die to seat .224 bullets. The heavy ones, anyway...
If you don't think a .22 caliber can be "better" in the wind than a 6mm, you
really need to shoot a fast twist .22 hotrod! It will make you a believer in 3 shots, or less...
Not taking anything away from the 6SLR, I think that cartridge is a super design & have pondered building one, myself. Likely, its a 'better' use of 243 brass, than the .243Win is. But, for ease of use/loading, & performance gained, stepping down to .224 for varmint detail is the path to happiness, IMHO. Side by side, there just ain't no way that a 6SLR can beat a .22-243Win in mid range trajectory or wind bucking, for varmint shooting...
Just some food for thought!
All depends on what you want! Zip around in a hotrod for ~1200rds, or drive more economically in a 6SLR for a couple thousand more. Both will kill the heck outta whatever varmints you choose to unleash them upon...
Have fun!