like what exactly? i read the whole thread and except for not having the right graphics card your only other problem i spotted was the i210. the latter should be sorted with AppleIGB which is even available for 10.5.
i plan on using 10.6.8 with a Z10PA-U8. if anyone is interested i can report back on how that worked out.
quick feedback here, things are running fine. i'm writing this with an E5-2690 v4 and 10.6.8 and i had no issues at all. in fact 10.6.8 was the easiest and 10.12.6 the hardest because the latter requires a pci patch. otherwise you're stuck in a reboot loop.
10.8.5 turned out to be a bit of a diva as well but needs almost no kexts and has no showstoppers like the 10.12 pci issue.
bottom line is if you wanna max out 10.6.8, broadwell is your best bet because it's the last with usb 2.0. use a supported graphics card, throw in voodootsc and appleigb and if you don't wanna mod the kernel yourself use the one from iboot.