There's no significant biomechanical improvement to be had over an upright with drop bars IMO, in terms of the power produced at the crank... except maybe for a return to Shimano's dropped pedals, and there could be a few percent in ovoid chainrings, but only if the aspect ratio is so great it basically rules out front shifting.
The problem of course, is that the most powerful position is a poor aerodynamic package. That's the compromise.
Certainly not every conceivable variation on recumbents has been tried, and IMO they're a vastly under-used format, but I'm pretty sure they'll never climb like an upright.
Also, try building a recumbent that weighs six kilos... or bunnyhopping one.