I also am not sure that Signature are the main culprit. As noted above the 'club' has had more owners than my grandad's shovel had handles. Mostly it has been run as a sideline by people with an aviation interest but no overwhelming drive. So depending who was in charge things have varied immensely.
Its last silver-ish era was when Bill Hendersen managed it for Tayside but that unfortunately is a long time ago.
Signature themselves probably barely have a business if it were not for the fuel. However hopefulyl someone will step up to the plate and try and make a go of it....