Just an update on things.
Deleted the Thunderbolt kext and it boots quick now.
Also was able to share a RAID set between OS X 10.10 and Win 8.1.
I bought 2 1Tb Seagate HDD's, plugged them into the SATA Express ports and created the RAID in OS X (Mac OS Extended (Journaled), with mirroring.
While still booted into OS X, I copied from my old PC drives all my Documents, Music, Videos and Downloads to the RAID set.
Booted into Windows I installed the latest version of MacDrive Pro and the RAID set is visible and usable.
So now iTunes(OS X) is pointing to my music collection on the RAID, and MediaMonkey(Windows) is pointing to the same music folder. Life is sweet!
I did however needed to create separate downloads folders on the RAID to keep the .dmg and .exe files separated.
Almost all apps work. Adobe CC, FCP 7 & X, MS Office, etc.
The only apps that have a problem are ones that are still incompatible with OS X 10.10.
I'm still planning to add a BD-DVD-RW drive.
I'll post an update to that if I have any issues with it.