The Russian Buran was the best design.
Buran is a large shuttle capable of lifting over 30 tons, but like you suggest, the main engines are not mounted on the orbiter. The Russians designed a heavy lift launcher AND an orbiter. The Energia could be used as a stand alone HLLV (capable of lifting over 100 tons) without the shuttle. This gave the system multiple uses, and made it far more flexable than our shuttle.
The only engines on the Buran were OMTs and de-orbit motors. Plans were also in the works to mount turbofans on Buran to give it greater flexablilty during landing.
In German, but you get the point.
Could be used as a HLLV and shuttle launcher.