Strange you should ask. I'll be keen to see what ideas you come up with re vibration alarms. As one of my other passions is motorcycles, I'm are of a few disc locks with loud vibration alarms - of course, they don't HAVE to be mounted to a disc, so I'm scratching my head at the moment re options.
As far as locks go, the beauty of ebikes is that you can consider some very heavy locks that you might otherwise dismiss. I use the Kryptonite New York U-Lock through the seat stays & rear wheel, locked to something solid, coupled with an Abus covered steel rope thingy looped from the lock through front wheel & seat rails. The serendipitous bit for me is that the New York lock fits snugly into the bottom of my Carradice Super C Rack Pack without bouncing around. So snugly, in fact, that I have to put it in the right way round.