I've seen plenty of RT. angle SATA cables (data). Power would be a little harder, but there's a connector type (Insulation Displacement) that is meant to be pressed into a 5 lead ribbon (18AWG). Two covers are available; one allows you to terminate the end of the wiring, while the other allows you to place it in the middle (feed through). You should be able to use 4 wires, unless you do want to run the staggered spin up line. (I'll have to hunt for the parts, so hopefully, I can find them. The one's I have on hand aren't marked).It looks like there is if elbow connectors are used or if I use my own mountable connector caps - like Apple itself is using on that backplane brace bar thingy.
I'll know more when I get into it.
So doable I think.
Found them:
IDT Interconnect
IDT Feed Through Cover
IDT Recepticle to Feed
I didn't see anything like these for backplane connectors.