I'm not sure if anyone has tried it, and if they have, it is highly unlikely that anything would have come of it.
Some very closely related species (from same genus) can hybridise and people have bred them and produced hybrids. However, crossbreeding species and creating hybrids is frowned upon in the scorpion keeping hobby, so be prepared to get a hell of a lot of stick for it if you do try.
I don't know how you would test emperor scorpions for strength and breed this 'trait' into the next generation but you may have success breeding larger emperors if you can source some large individuals to start off with.