The only stand available to the 767 at BRS is 26 and that is right at the end of the western pier. Not really suitable for premier operations at present. Not sure if the extra wing span would fit on 26 but not too much trouble to create a rarely used stand for a large aircraft that simply integrates several stands in to one. Lots of airports do that.I remember Bhx used to do it when the air India 777 came in. They just used a standard stand but had to close the stand either side. As it would be a rare visitor I doubt no solution could be found.
More than likely with the changes in weights, specs, perf, etc... The 787 has undergone whilst under painful development it has reached a point where the promised short field performance has not been possible. BRS has done commercially very very well given it's runway limitations but you do reach a point where you have to accept it just isn't long enough. I suspect that point has just been reached