6) Modify a PRS Trem
Because the tremolo block can be unscrewed from the top plate, you may be able to wedge an element between them like the video below. This might be worth experimenting with since it’s completely reversible and the elements themselves are only about $5.
8) Q-Tuner Magnetic pickup
You may be able to add an additional Q-Tuner magnetic pickup, which has a large dynamic range and more capable of capturing an acoustic sound, especially when combined with something like the Fishman Aura Imaging DI.