You can remove the Expressway option from your VCS be deleting the "Traversal Server" option key under Maintenance > Options Keys. Once done, that will turn the VCS into a Control, if you ever want to make it an Expressway again in the future, just take note of the option key so you can add it back.
Note, the removed option key will work only for that particular VCS as it's tied to it's serial number. Which means, if you install this "new" VCS which is currently an Expressway that you're going to turn into a Control to replace you're "old" one, and you find you need an Expressway for whatever reason, you can't take the old Control and use the removed option key from the new one. It's best if you have a like for like VCS, meaning almost simliar option keys and/or features you should use that.
Something else to note, since you're running VCS clusters, you'll want to be sure the install option keys across all VCS are the same (such as FindMe), if one has more than the other than you should remove the extra ones. Non-traversal and Traversal call licenses don't count with what I just said, you can have any number of those, it doesn't matter, it's just the option keys that add "features".
Since you don't use Jabber Video (Movi), that's a plus, which means unless you're using TMS to provision your physical endpoints, you shouldn't have a problem upgrading when you find the need to. Suggest you take a look through all the release notes from the version you're running to the current release, give you an idea of what's changed and what to expect going forward.
