My tripod, a Gitzo 1325 mk2 has recently gained a fair amount of weight.
Life was good, well mostly anyway for a long time. I had an Arca Swiss B1 ballhead mounted to the top plate of my 1325.
Then I got a Wimberly sidekick to facilitate birding and I quickly found that if the tripod head wasn't level it really has a hassle so I added a 1521 leveling base.
This brings up a couple of concerns.
One it seems that the 1325 has the same design challenge as the newer Gitzo's where the top plate is not secured below the frame and the pressure applied by the clamping system can be the only thing holding the leveling base to the tripod since you can no longer secure it from underneath with any of the 3rd party solutions available.
The second is that the 1325 isn't all that light in the first place, add an Arca Swiss B1, 1521 leveling base, and sidekick and it is downright heavy.
I don't think anything heavier than say a 100-400L or Sigma 120-300 with pro body will end up on it.
I do use this rig for both wildlife and general photography so I expect to have bodies with L bracket's attached to some type of ball head in addition to the sidekick with long lenses.
I'm thinking of change to a much lighter setup and am not aware of any downsides so I thought i would ask before screwing up.
I'm thinking of going back to the std top plate and Arca Swiss leveling base, and appropriate Acratech head and would appropriate advice whether or not this would work, I would also be adding the 3rd party plate to secure the top plate to the tripod base.
How far are you packing your rig? I have a similar set up to yours 1325, 1321 leveler, Wimberley 200, 500 f4 L IS with 1.4 X II and 7D. Very strong and vibrations resistant set up IMHO and I pack it up to three or four miles up and down reasonable mountain trails. Sure it is a bit heavy but it is worth it to me to have the strength and stability it provides. I will be 65 next month and am in fairly good condition and "knock on wood" I hope to be able to pack this rig around for several more years.
Before moving to the Arca-Swiss Z1 with the Wimberley Sidekick, I used the Manfrotto gimbal head. It's light and very good, but not quite up to the Sidekick. With the lenses you mention, I'd work very nicely.