Well, this escalated quickly.

Trying to get more interesting worldspace-based effects happening (basically, a ripple would be nice) but until then, these unforeseen behemoths sure are interesting. The hotshot line is:

ico.geometry.vertices[i] += Math.sin(clock.getElapsedTime() * ico.geometry.vertices[i]) / 2;

(for all axes individually)

[everyday 5/28/17]