Very interesting! Please let us know how the modified BP100 works for you.
Darkfinger: I feel your pain, feedback is sooooo frustrating.
I think 90% of the problem can be solved with a properly installed pickup (ie RSII, Underwood or Bassmax) and a preamp with HPF and invert phase (ie F-Deck HPF).
Proper installation is critical. The wing surface and the leg should be perfectly flat, to maximize the wood area in contact with the pickup. The leg and the wing surface should also be parallel.
The pickup should be installed snug, but not too tight and not too loose. If the pickup is too tight it will become more prone to feedback and the tone will be choked. If the pickup is too loose you will not be receiving full volume from the pickup and tone also will be lacking.
An afterlength dampner is valuable too - I have a rubber band wrapped around my strings between the tailpiece and the bridge.