4. It Could Bring An Extra Dimension To Other Villains
The Master has a long track record of working with other monsters, in an admittedly loose definition of working with. Admittedly it often involves the Time Lord manipulating the other creatures to his own end or the other villains trying to trick the Master into playing into their hands. In the past there have been Autons, Daleks, Axons and most recently Cybermen. While in Dark Water the threat of Missy does end up diminishing the threat from the Cybermen (theyre more like her weapon than an adversary in their own right), the renegade Time Lords team ups dont always go that way. In fact, it would be an excellent opportunity to bring back classic and even NuWho villains and give them a different dynamic through teaming up with the villain. Thered be an easy receptacle to bring back the likes of the Wirrn, the Sycorax, the Macra - the less iconic villains who are worthy of another day in the sun nonetheless. Thered also be the chance to give some of the ones that feel tired a fresh dynamic. What if there was Cybermen ready to hunt down and kill Missy based on the fact she used them as her foot soldiers in Dark Water? How better to freshen up the Daleks - in NuWho, at least - than by pairing them with another villain on their level, since theyve mostly been on their own as the big bad with the possible exception of the coalition in The Big Bang? How on earth would the Weeping Angels even manage to team up with someone? Ok, maybe not that last one. These team ups wouldnt just be able to bring these races back with fresh dynamics but they could even allow for a further exploration of their mindsets and motivations. The writers would be showcasing how they interact with an ally/adversary other than the Doctor so its possible fans would get to see a whole new side to the aliens they know and love to hate. Thats definitely something that would be exploring.