Are there any SAN vendors that allow third party drives? [closed]

The HP P2000 SAN units can accept SSDs in their D2700 expansion enclosures. That's a decent way around this. The P2000 itself doesn't officially support SSDs, but people use them anyway.

12 x Corsair Force GS 360GB, no problems recognizing them. That's why I chose the HP, no drive restrictions or firmware locked crap.

But rather than put the SSDs in the SAN, have you considered host-based caching options?

Another approach is to use a tiering solution in front of your SAN. Use a NexentaStor box loaded with several SSDs in L2ARC to tier your hot data and keep the existing SAN for bulk storage.

None of the big ones no, why would they? most of their margin comes from the mark up they make on drives. That's why there are software-only SAN solutions such as FreeNAS etc. that DO let you use whatever you like. The world needs both markets.