This is one (rare) time that I would disagree with Bizresearcher.

Starting a new line of almost anything that already has a big name player is pretty well doomed from the start. "Mocktails" are already being done by the big names. Tyring to sell onsies twosies like Bizresearcher suggests is a waste of time, money and energy.

I wasn't quite sure what you meant by "wedding proposal planner". You mean you would plan the actual proposals? Like sky writing a proposal? If that's what you mean then I would say AWESOME idea. Go for it! A regular ole wedding planner? Eh, not so much. They are a dime a dozen.