I have been looking in to a .22-6mm Remington mostly because I have plenty of brass and would like a fast twist .22 cal shooting 75-80 gr bullets, in a long action to take advantage of the 80 gr v-max etc.
.243, 264, and 22-250 have Lapua brass, and I think if I didn't have plenty of 6mm brass, I would look at the 22-250Ai or the 243 midland,
Don't really see any real advantage to the .22-284 as it seams to be well beyond the capacity of the bore, more powder for no real increase over the .243 and 6mm case size.
I want to build one for goats and fallow deer, and cross gulley shots, in windy conditions, ( common hunting problem in the area of NZ I have my house) hence the high BC bullets being pushed fast, currently use my .264 win, but it's a bit much on 50-75kg animals.
Starting to lean on the 6mm Remington AI again, mostly as I have a couple that could be reamed out to Ai for bit more performance.
I wish the 22-250 was much more readily aviable in a fast twist, Sako and Winchester are you listening.