I'd be surprised if there wasn't about a 50/50 split in opinion between seeing it as more boring to play the teams you mention, or playing the top flight teams twice as often.
I tend to prefer the variety personally. I'm much less likely to go to see us play Motherwell 4 times than them twice and Dunfermline twice.
it's not so much WHO I'm watching us play that is the factor for me, but HOW we're playing. Each team is a different challenge in terms of tactics, personnel etc, so it's of more interest to me.
An extra 6 teams wouldn't really make the cup less interesting as when you do draw a top flight team, that in itself is exciting because, in place of the variety, it's more of an unknown prospect whether we'll get through.