Cheaper option then what? Out of Dublin, there's plenty of direct routes on Ryanair or other carrier to popular holiday destinations, and I wouldn't be surprised that with some advanced planning that a fare + options could be lower then what M&M would charge just for fees. And since LH&Co are nothing to write home about, having a direct flight is quite a bit more enjoyable then connecting at either LH hub.

If you're hell bent on just burning your miles then go ahead, but local flights represent a pretty poor value proposition.