Recapturing side and back lobe radiation from a directional antenna
The most efficient way to capture and re-radiate is to add more material (metal or, in some designs, dielectric) to reflect or diffract the radiation — and that's what designing a higher-gain antenna is. Make the dish bigger, add more Yagi elements, et cetera.

Anything that is “cleverer” than that will be bigger or lossier than simply improving the main antenna.