With Thunderbolt 2 / USB 3 support, I suspect some enterprising manufacturer will come up with a stackable storage enclosure that matches the design of the Mac

With Thunderbolt 2 / USB 3 support, I suspect some enterprising manufacturer will come up with a stackable storage enclosure that matches the design of the Mac Pro. That would meet all your storage requirements while keeping the size down for those who only need the additional performance.