ok, here's an idea that someone might either build on or refute: would it be possible to build an amplifier of gravitational waves using some arrangement of microscopic and/or macroscopic objects having a "known" defined 3D physical relationship (say in a lattice), and under known interactional forces (including EM). You would have to take into account the uncertainty principle in system parameter measurement, though the propagating gravitational wave should have a deterministic effect on the potential well and thus the quantum wave(s) of the system(s). Thus, amplification through propagation in the space-time of the system might be feasible. This is of course all hand-waving, and very rough.