So i'm just in my normal day and it just pop to me. How about having magnetic pickguard? Buy some very thin neodymium magnet in pair (2mm for diameter x1mm) and make some hole in your bass (probably in the unfinished one) with 2mm diameter x1mm depth. Then make the hole again in the pickguard for about the same size in a matching place. However this is just a thought of my self and i have never made this. But maybe i will in future. Please leave your comment!