Yup, someone thought of it. That man's name? Buzz Aldrin.

https://buzzaldrin.com/space-vision/rocket_science/aldrin-ma...

https://web.archive.org/web/20101102073607if_/http://buzzald...

It is indeed more efficient to perform the usual Hohmann transfer, but the advantage of the Aldrin Cycler concept is you can accelerate a large vehicle once and then 'amortize' that over multiple trips.