Tag indirection in Client Tag Change Script

We have multiple machine in our project and each area is going to have a separate gateway. Once we develop the project on development server, we will push it to different gateways using EAM module. We have used multiple Client Tag Change scripts in the project. I have 2 questions regarding Client Tag Change script:

  1. Can we use the indirection in the tag path

We will use the gateway name to differentiate the area name. Rest of the path will remain same. (We will manually change the area name in the tag browser during setup). But since there are multiple such script which we will push to different gateways, it would be easier to use indirection (probably like expression - '[default]Enterprise/Site/' + {[System]Gateway/SystemName} + '/Machine/TagName'. But this doesn’t work. Is there any way to use indirection in the tag path here?

  1. If there is a script here which can take longer to run like fetching data from DB, can it slow down GUI? Basically does it run inside the Event Dispatch thread and using invokeAsynchronous will be useful?

Thank you in advance.