Hi,
So just to make sure that I’ve understood your requirement correctly: you want to prevent Resume from being used on multiple selected objects, execute the Resume action, and then run some additional logic after that.
In that case, I would avoid hooking too deeply into the default Resume action. It can quickly become fragile.
I would rather create a dedicated custom Resume action in an ICN plug-in, hide or replace the standard one in the target menu, and control the enablement there.
So if more than one item is selected, the action is simply disabled. Then, from your custom action, you can call the Resume logic and execute your additional processing in the success callback, or server-side through a plug-in service if it must be guaranteed.
So yes, a custom action might sound like the right direction, but I would treat it as a clean wrapper/replacement of the OOTB Resume action, not as a deep customization of it.