Sorry mate you can't guarantee anything. I know you probably weren't around in the early 90's when we were challenging for the title and our average attendance barely rose beyond 7K. I appreciate that is a significant increase compared to today's average, but we had a larger latent support at that time too. We couldn't even sell-out a Champions League game recently. We just don't have the support, or interest I think you think we have - success or not.
I used to watch in awe, when Aberdeen used to make cup finals and challenge - and win league titles - and used to tell my dad, how big a support we would have if we had similar success. His comment "you're aff your heid" - sadly he was right.
The only way I think what your suggesting would happen would be with a healthy sustained period of success/challenges and that ain't gonna happen, with or without the "Old Firm".