Is there a rectifier scheme for tri-phase which is more efficient than the bridge rectifier?
The energy efficiency of a three phase rectifier is pretty high in my book but if you're only wanting to push energy into a resistive load then make yourself a star-connected load of resistors. This will be perfect - no losses in diodes at all.

If, on the other hand you are requiring a DC output then consider what high power switch mode power supplies do - nowadays they have to correct for surges and non-ideal power factors by trying to utilize energy from the input waveform all the way along and as such they "strive" to present a near resistive load to the incoming AC.