James,
It seems like a very good idea to have two different power supply options, so the unit can be used by folk who don't own BP25/26. Also, BP25/26 owners would benefit from powering the headphone unit via MPS2. As there are more and more volk who listen only quality source via top headphones today (no amp and speakers), I believe the unit could have positive effect on BDA-1 sale, which is great for you.
Personally, I would like to have more serious headphone amp to drive my Grado RS-1 and as you are company which knows how things should be amplified, I would be very interested to own BHA-1 or whatever you call it..

Best,
oz.