The Gaoersi 6x17 does all three but I really cannot work out how you frame count for 6x15, as 3 x 4.5 is 13.5, and there are no frame numbers for 6x7.
I actually do like the 6x12 format, and also have some 4x10 FP4+ ready to use, I just need a way to secure it into a 8x10 filmholder.