"Very easy to get the BMW engine over 500bhp, now whether its drive able is another question ...."
That's the key bit isn't it. Adding power is something I love doing but there comes a point when it reduces your enjoyment. The only car I have ever had that just took more and more was a Skyline GTR33v which at 600bhp still felt like it had capacity for even more.
I think with the Plus Six it would be more likely that you would want a map to remove the dead pedal low RPM response due to emissions mapping and then reduced the lump of torque arriving in the first 1300-2500 rpm segment to make it more adjustable. I can see that making an improvement, perhaps another 50bhp at the top end for bragging rights and a good giggle once in a while?
