The Three Timelords (Tenth Anniversary Special) (1973)
Having different incarnations of the same character meet has always been a tantalizing yet ultimately annoying thing for me in Doctor Who. I can understand the temptation however - an evocative way of celebrating the past of a show is to bring together elements of its past and in the case of Doctor Who that can include past actors who have held the title role. But there could be other ways to do this and so I would have liked to change the story The Three Doctors as follows:
In order to prevent the exiled stellar engineer Omega from seeking revenge on his civilization, the Timelords, they would manipulate the three renegade Timelords so far known to exist on Earth to work together, those three being the Doctor, the Master, and the Meddling Monk, a character from the time of the first Doctor.
Planet Of The Cybermen (1973)
A pattern I have discerned in the original series was that each of the seven Doctors had encounters with both Daleks and Cybermen. Well almost. The third Doctor never had a Cyberman story while also having had three separate Dalek stories. Since my teens I have imagined one of these serials in revised form as a Cyberman story. Any one of those three Dalek tales could have been a Cyberman tale with some re-working of concepts and characters. I think the simplest and best to alter in my personal imaginings of how it could have been is Planet Of The Daleks.
In the final scenes of the prequel story (Frontier In Space) we would see that the clients the Master had been working for were the Cybermen (using the Invasion serial costumes). They are intent on both conquering the Terrans and destroying the Draconians once they have fomented war between those two powers. In Planet Of The Cybermen we would then see that they have returned to excavate Talos and free the frozen Cyber Legions stored there. Talos can still have an "ice volcano" on it (as does the planet Spiradon). The Thals (who surely the Daleks exterminated long ago) in this story can be replaced by a combined taskforce of Terrans and Draconians. Finally back in Frontier In Space we will see that the Ogrons truly are mercenary as they will have worked for both the Cyberman and the Daleks (in the older story Day Of The Daleks).
The Invasion of Time (1978)
This fourth Doctor story involved Sontarans infiltrating the capital on Gallifrey. However it always seemed that the Sontarans lack the stature to do such a thing. It is one thing for the Daleks to engage in a Time War but the Sontarans seem more a middling power and one that is busy permanently engaged in war with another middling power in the Rutans. I would replace them altogether with the Warlords last seen in the second Doctor story The War Games.
The Warlords are human-like aliens who are familiar with the Timelords and space-time manipulation. They also have the desire for revenge once the Timelords scuppered their plan to produce the ultimate army from all timezones of Earth history. They would work well in this story and if less were spent on alien costumes then more could be spent on TARDIS room sets. And yes I may be reducing the tally of Sontaran appearances by one but you will discover I intend to increase the incidence of Rutan appearances by the same number.
The Tomb Of Rassilon (Twentieth Anniversary Special) (1983)
I have pondered The Five Doctors rather a lot and my revision involves replacing all incarnations of the Doctor (but the then current fifth Doctor) with companions and allies of all past Doctors and then have them experience similar action as in the Five Doctors special. Consider the following...
* Susan (grand-daughter of the Doctor who travelled with him during his first incarnation) has outlived her human partner on Earth and decided to regenerate. She bides her time while human technology improves till she can acquire a one-person faster-than-light space craft and wander the galaxy hoping to find something more interesting and possibly even get home. In a tendency more characteristic of new Who she will have been cast as a well-known guest actor - say the Joanna Lumley of 1983. She gets her wish of returning to Gallifray but in a surprising manner as her ship is forcibly timescooped into the Death Zone. There she meets another past companion...
* Jamie (companion of the second Doctor) is hunting in a glen but is timescooped into the Death Zone and soon meets Susan. They have never met but decide to work together and soon come across the TARDIS - this prompts conversation revealing that they both know the Doctor (the sight of the TARDIS forcibly reverses the memory block Jamie had been suffering). Later they find and decide to enter the tower from above and encounter a lone Dalek as they do so...
* The Brigadier and Jo Grant (an assistant of the third Doctor) are taking the vintage car Bessie for a ride for old time's sake and get timescooped into the Death Zone. The car tires are soon shot at from the roadside by an alien - The Draconian Prince. Luckily Jo remembers him and prevents combat between him and the Brigadier. They all agree that the Doctor must have something to do with this and go looking for him. They decide to enter the tower via the front entrance but must get past a group of Cybermen...
* Leela and K9 (Mark I) have lived on Gallifrey since The Invasion Of Time but things have changed. Leela divorced the Captain of the Guard once he regenerated to better fit his new role as a Council member. She is at a loose-end and had a tendency to snoop into secretive matters. These two therefore are also dumped into the Death Zone. They find a way into the tower from below but must overcome two Zygons who can impersonate others - the fact that one of them pretends to be President Borusa suggests that they have met him in those catacombs...
* The Doctor and his current companions Tegan and Turlough are also drawn into the machinations happening on Gallifrey. Likewise recurrent enemy the Master is involved but there is another enemy behind everything...
I think this all works rather well in representing the five eras till 1983 with interesting characters (including among the companions both a robot and a visibly alien ally). Each group is also resourceful by itself. And in the Zygons I present a creepy monster that only had one story but was supposed to also appear in the never-completed story Shada.
The Two Doctors (1985) was a silly sixth Doctor story also involving the Second Doctor seemingly just coz. The returning adversary in this story was the Sontarans. The whole thing is a bit naff and one missed opportunity was the chance to present an encounter between the Sontarans and their nemesis, the Rutans.
There was however a Doctor Who spin-off telemovie made in the 90s called Shakedown. In this story a solar sailer on its shakedown voyage is commandeered by Sontarans seeking a Rutan spy which can assume the form of anyone it kills. This could have been a sixth Doctor story. And it was in fact made into a Seventh Doctor novel.
Well that is my messing with the Doctor Who canon for now. I apologise to all those who cannot understand this because they have never seen all this old stuff. It is jolly good fun even in its original form. I wonder now how much the Fiftieth Anniversary special will satisfy me or conform to my notions of what makes a good Doctor Who story.