There should be a Bundle Tab in the Crown Shop, where you can see all Online Bundles and if you want to, be able to buy them with Crowns that you ALREADY have. If they're on sale, they should reflect the discount as well. Don't just bring them in for a while and pull them out. They should be permanently there. You also should have a sub category for individual bundle items that should have crown prices as well. This will definitely encourage people to buy more stuff with crowns!
They'd have to adjust things a bit, bundles come with crowns. They won't make them permanent crown items regardless. The nature of the bundles and sales are that they are limited time only. Making them permanent crown items and available as pieces would lower sales. That's just not how successful marketing works.