I would add that it's quite an interesting problem in its self to decide what tasks are even in a wedding and what needs to be done. Maybe my idea is a little different in that it's focused around having control over all aspect of your wedding from the companies through to who will usher people into the church and what hymns will be sung...

This then makes me start thinking are there differences in the planning of a gay wedding, a baptist wedding, and Indian wedding...

Imagine if you could assign tasks and roles like groomsman/brides maid and you can agree to help out...

There's millions of possibilities with it... Even things like seat planning. Could be a lifetime of work.

Charging for the budgeting feature and allowing people who had already overspent by the most access to special offers by tradesman. You would have to be careful to filter out offers that were already being used!