Here's the first draft of an initial array for a chess variant that combines the more interesting features of 3 well-known large board variants: Omega Chess, Tamerlan Chess (a historical variant that has also been called Shatranj Kamil and Shatranj Al-Kabil), and Gothic Chess. Gothic Chess is an improvement upon Capablanca's Chess, which itself is a re-invention of Bird's Chess and/or an older variant by Carrera.
The rules for this variant basically write themselves. The "pawn of X" promotion mechanic comes from Tamerlane and Chaturanga. The other new pieces are directly adopted from Gothic and Omega chess. The only real questions are the castling rules, any special rules regarding the wizards' corner spaces, and the pawn of king promotion. For the latter, the easiest solution would be for the pawn of kings to promote to Men, i.e. non-royal kings. I am also considering using the Prince, which is a similar piece but in this case the prince would also have to be captured or mated to insure victory.