Chris, that's a good idea... but like most, it's not new. We had a boat built in 1982 with exactly that setup - a 24 foot dayracer that raced one-design with the motor below on the cabin sole. We had the exact same type of bracket that accepted the more standard lighter duty spring loaded OB bracket.
We left the motor on the bracket and lifted the whole assembly off the slider just as you plan to do.. there was a keeper pin to prevent the motor/mount from 'hopping' off the transom on a big wave.
Nevertheless, good thinking, and nice work - should work fine!
You wouldn't happen to have any pics would you? I'd love to see another design on this idea.