The optional base GSX jetway is just about twice as long as the default jetway
The model GSX replaces default jetways with is *exactly* the same size of the default one, and it cannot be any other way, since they must match the default airports. This, of course, is only valid if you are replacing a default jetway on a default airport.
If you are replacing a jetway in a 3rd party jetway, you have the choice of the model. And, of course, if you downloaded a GSX profile made by somebody else, he chose a jetway model.
The other side of the problem is, when I land the aircraft at CYEG ground control keeps assigning me to gate 10 which had no default jetway or passenger bus service.
If with "ground control" you mean the default ATC, that doesn't have anything to do with GSX, which doesn't change which gates the default ATC will assign you to. Not that it would made any difference if you meant something else, such as 3rd party atc products or human controllers, which also GSX has no control over.