se326m1 hardware modding

[ired]

Hi, 

I bought a SE326M1 server (very similar to DL180 G6) which I plan to use for homelab desktop virtualization.

CPU and RAM didn't arrive yet, so I didn't turn it on yet but I have a few hardware modding ideas
Remember, this is home project, so "unsupported" and "wouldn't do this in production" are beside the point :)
I'm asking for your opiniton on whether this is feasible, will it/does it have a chance to work or other ways I should consider to reach the intended result.

It's a 25xSFF version, p410i raid controller, 1x x16 riser on the low profile side , 2x x8 riser on the other

I have several problems with the raid controller:
Ideally I would want to use 3 pcie cards:
 - 1 video passed to linux vm
 - 1 video passed to windows vm (probably 2 slot wide preferred)
 - usb 3.0; and the raid controller occupies one of the slots
Also I plan to use zfs and p410 doesn't have direct JBOD mode. While possible to create single-disk raid0 volumes to "emulate" JBOD mode.

Considering the pcie slot "stolen", the best solution would be to somehow drive the 25xSFF backplane from the 6 onboard SATA ports. Note that I don't expect or need high IO bandwidth, so having like 6gbps total bandwidth to the hdd backplane would be acceptable. I don't plan to use anywhere near 25 hdds, but I wouldn't like to be limited to 4 or 6 either.

Does connecting 4 sata ports on motherboard to the backplane with a cable like this
have any chance to work?

Another modding target is the full-height riser card

ideally I would like the lower 2 slots be occupied by an upper-medium performance video card (R7 370 is the most likely candidate) which I will pass through to the windows vm. 
But then the upper slot being not connected I'd need a 3x x8 riser like this:

My question would be: 
Suppose I get a custom circuit manufactured which directly wires the left x16 into a x16 connector in the middle slot and the x4 connector into a x4 (or x8) connector in the upper slot.. 
Note I'm talking just direct wiring, no circuits..
Would this possibly-probably work?

[Unlimited1980]

Are there some news from your project?