That is a really nice piece of gear, and i would not skimp on any accessories for it.
That said, I really like my Wimberly sidekick. It converts my ball head to a gimbal in a few seconds. Much faster than swapping a whole tripod head. This means I can carry just one tripod. And at 1.3 pounds it's a much lighter addition to my travels than a separate head, or separate head and tripod.
Obviously it must mate to a high quality ball head. Mine is great and the combination has been great with my 400mm f2.8 IS.