Gig Performer is straight forward and rock solid.
this suggestions would impact the whole design.
Is there any showstopper in the actual design?
There are ways of getting close to this concept by either: 1) putting the plugin in the Global Rackspace or 2) reusing rackspaces where you have a plugin with the sound exactly as you want it (subject to plugin tweaks using widgets).
For plugins/sounds I reuse a lot, especially if they are memory intensive, I put them in the Global Rackspace.
But, there are some plugins are might reuse, but not that often. For sample-based plugins in this category, I try reuse that rackspace, while bypassing plugins that are not needed. This may include adding some new plugins that are used on an new song but were not in the original rackspace. So, you want to make sure the new plugins are bypassed in the original rackspace so they do not mess up songs associated with the rackspace before the changes were made.
So, you have to be careful, because you do not want to mess up prior songs that use that rackspace.
If you want to go the latter route (option 2), I recommend you read through this thread and consider downloading/installing Vindes extension.
Basically Vindes walks through a procedure to follow if you are reusing a rackspace to access a plugin/sound use there (to save ram). Always bypass any added plugin in the original rackspace, then you can un-bypass them using a widget for the new song.
Also, if you are bypassing an existing plugin in the new song, that should be done via a widget in a new variation. You should double check that the plugin is not bypassed in the original variation (and in the original song part).
The extension is basically a safeguard so you can find and double check that all songs that use that rackspace are still working as expected.