I don't see why there are two queens and only one colour bound caliph. I asume it is for balance but maybe something else could be done as from an artistic point of view it does not make much sens. What about caliph's on the starting squares queen squares as you have drawn them and instead of your central caliph a more powerfull queen. If you are ok with the many bishops moves, maybe BDHN would work fine. This is obviously a first glance judging and not a thorrow investigation :)!
@Greg
I don't see why there are two queens and only one colour bound caliph. I asume it is for balance but maybe something else could be done as from an artistic point of view it does not make much sens. What about caliph's on the starting squares queen squares as you have drawn them and instead of your central caliph a more powerfull queen. If you are ok with the many bishops moves, maybe BDHN would work fine. This is obviously a first glance judging and not a thorrow investigation :)!