In my review of the episode I admitted that I did believe Mels might have been a new companion. In those opening scenes I could imagine the changes she would bring to the TARDIS crew dynamic and the exciting adventures this might lead to.
It was all a brilliant misdirection by Moffat but a similar character could appear in your own Dr Who roleplaying game. This might even happen organically if a player runs their own character with such wild abandon and wilful disregard for history.
Ironically, it is Mels’ own desire to kill Hitler than saves his life. Had she not forced the Doctor to the 1930s the Teselecta would have been able to complete its mission. This is a good example of where a time travellers intention to change something can actually make it occur.
This is useful because it is one tactic to use when player characters try to do just that. For example should they try to go back and stop a villain from carrying out an evil plan they could find that person in question has no idea what they’re talking about.
When the PC explains in detail what they were going to do does the villain agree that it is a brilliant idea and put events in motion. Had the player character not gone back then the plan wouldn’t have been thought of.
Mels idea shares similarities to the Teselecta’s mission, which the Doctor comments on later. Why would you use time travel to punish dead people? Is the motivation to save people or is it just to make yourself feel better by inflicting harm on a figure of evil?
The ‘Doctor Who Brilliant Book 2012’ expands on Mels obsession with changing history by showing us an essay she wrote in school where she details her imaginary adventures with the Doctor, punishing the wicked and making the past better.
It isn’t hard to imagine that this stems from her own hard life. Spending several decades living rough, her own parents not even being born yet, was bound to make her bitter. Who can blame her for wanting to change time?
All of which can be used as justification for PCs and NPCs will similar temperaments. The Doctor and his companions are usually content with their lives and so have a desire to preserve their past.
Having a new companion who wants to make a difference can add new complications to adventures. The question would then be how do you run such a campaign without in-game friction causing real world arguments.
In the episode itself it is the fact that Mels has a weapon that forces the others to comply with her wishes. This is certainly one way to handle the situation in-game. This would be especially effective with a NPC Time Lord piloting the TARDIS, especially if they are more like the 1st Doctor than the 11th.
This status quo would be hard to maintain as the companion is basically a villain. The other characters would naturally look to find ways to remove the hijackers weapon, escape or abandon them the first chance they got.
In a reflection of ‘Doctor Who’s attitude to weapons it is Mels who ends up getting shot. This is a good indication that those who live by the sword should die by the sword (or at least be very badly injured).
Another way to go is to have the Doctor (or Time Lord character) try to educate the wayward companion. It is entirely possible that they could be shown that what they want is futile and there are better ways to help people.
For this to work the player must agree that their character’s attitude will change, following a character arc as the campaign progresses. Their agreement is important because otherwise they could feel they are being forced to change their concept.
Adventures could bring them into contact with other time meddlers to illustrate the dangers of changing events. They could help save people during historical events showing the good the time travellers can do without changing the event itself.
The attitude of the Time Lord character can also have a big impact on the situation. It is easy to imagine the 7th Doctor using a person like Mels as a tool in his crusade against evil, directing her anger towards a useful purpose.
Much like Ace Mels violent tendencies and criminal past could be exactly what the 7th Doctor needed in his more morally dubious missions. All that would be required was to place her in time periods where she couldn’t affect historical events.
In adventures like ‘The Happiness Patrol’ Mels would have a great time dismantling the tyrannical government of a colony. The Doctor could even mislead her by telling her false facts about the future to make her believe she is changing history.
A games master could also just embrace the companions nature and allow them to change history. This could lead to a scenario like ‘The Wedding of River Song’ when they alter a fixed point in history or an alternative timeline which is far worse than they imagined.
The companion just might learn the errors of their way and set about fixing things and making sure that no one else tries to do what they did.
Whichever approach you take a companion with a different attitude can help keep a campaign fresh and take adventures in a new direction.