it would be a sort of BP-26 / BDA-1 combination in one chassis?
Hmm... So... Why is it possible to add this DAC to an amplifier and not to the BDP? I don't see how it would be any different. Digital input on one side, analog output on the other side, I don't think it matters whether this happens in the BDP or in an amp.
So, add it to the BDP, create a product more people will be interested in, realize more sales.
Or add more output options. Like optical, firewire, RCA, USB, ect. My CD player has an optical input, if the BDP had an optical out I'd buy it.