There isn't an easy way, sadly.
Basically every reference to a Mesa card pin will cause an error on a machine that doesn't have a Mesa cad connected.
I think that some time ago someone made a "fake" 5i25 component, ie one that created pins with the same name as a 5i25 but without any of the internal functions.
But even that doesn't get the system working, as the command and feedback need to be handled, or there will be an immediate following error. And homing needs to be handled by even more logic.
It's probably easier to modify a sim config to be more like your gantry than to edit a real config to be more like a sim. To a large extent just copying the joint / axis section of the INI from your real machine to a sim config will get you rather close.
