This shows great creativity on the part of the guy. Absolutely nothing wrong with that. It doesn't make it better than any other proposal, but a fun memorable event for the couple. The way you propose has no bearing on how the marriage will do, so what does it matter if it seems too elaborate today.
I have heard that comment before "How do you top it?"... Who says you have to? Enjoy the moment for what it is. It's like saying don't attempt to make the best movie you have ever done, because how do you top yourself after that....... For this couple, today it is an elaborate proposal, tomorrow, it is a candle light dinner on the lawn in the backyard.... It is the creativity of the proposal that should be celebrated.
If she is the type of woman that expects each event to be better than the last, then there is something wrong with her perspective on life. And that will affect their lives in many more ways far beyond this proposal. Hell, you may not get the chance to top yourself... Show the ones you love how much you love them everyday! No matter how big or small.....
Tomorrow is not promised...
Try to live each day like tomorrow will not come.