I'm not sure about Season 27. Did anyone actually write scripts for it? Or did Cartmel just have an idea of where he was going?
Copied from a post on GB these are the ones that were under consideration, not including the Ace goes to live on Gallifrey story:
Ice Time by Marc Platt
Pieces of an incomplete alien suit of armour are being exibited at the London Dungeon. Somehow, the remaining parts are found and the suit is completed, this causes it's original occupant is to be reborn inside the suit: an Ice Lord. The Ice Lord has a rival who has been chasing him accross time. Now he has been awakened their terrible fued can continue, bringing devastation to Swinging London.
The Crime of the Century
The baby girl the Doctor Delivered in Sixties London has now grown up to become a beautiful femme fatal and international safe cracker. Arriving at a party for the super rich at an English country mansion, she works her way around the ballroom and up the stairs where she finds the safe. carefully she cracks the combination and opens the door. To her astonishment she finds a stange little man with a scottish accent inside. "What kept you?" he asks.
Alixion by Robin Mukherjee
The Doctor and Ace arrive on the planet Alixion, where an order of monks have decided to live underneath the surface of the planet, practicing a vow of silence and forbidden to cultivate friendships. The monks produce an elixir that enhances intelligence, harvesting the glands of the indigenous giant beetle-like creatures to create it.
Earth Aid by Ben Aaronovitch
A space opera featuring the Metatraxi, a species of insect like Samurai Warriors with a strict code of honour. The Metatraxi are confused by the Doctor, as they find the idea of fighting people who are unarmed dishonourable.
Avatar by David A McIntee
An etherial alien race is using the dead as vessels. Their leader has discovered the fossilised remains of a Silurian God and has plans to reanimate it.
Hostage by Neil Penswick
An elite group of soldiers are sent after shape-changing criminals Butler and Swarfe, who have stolen a new weapon and taken it to an overgrown jungle planet. The Doctor and Ace arrive and become involved in the hunt. The end of the first episode sees Swarfe change into a monster. It emerges that the planet was the last battleground between the Time Lords and the Scaroth (sic). After scenes set aboard a futuristic helicopter gunship, the action moves to a set piece in a fairy-tale style castle, where the criminals intend to detonate their bomb.
A School For Glory by Tony Etchells
Set during the First World War, partly in the trenches and partly in a British country house which would have been some kind of academy. It would have been highly critical of warfare and the butchery of the War, and see the class edge as the evil of it all. There would have been some alien interference in the form of possession by a telepathic force.
The Clockwise Cuckcoos by Matthew Saunders
The Autons attempt to invade Earth by infiltrating a TV gameshow, fiendishly replacing the smarmy host and his bimbo assistants with plastic replicas. Thus the Autons planned to transmit their insidious message into the homes of the viewers, activating deadly plastic clocks which had been distributed free of charge to gullible viewers.
There were also murderous ‘He-Man’-style dolls, and plastic spiders which came free in boxes of cornflakes. Sil also returns wielding a filofax and mobile phone and enjoying dips in his jacuzzi and trips around London in his limousine. UNIT were also involved, led by Brigadier Crichton (of The Five Doctors), and Lethbridge-Stewart was also called in to help out.
A comic scene would have seen the Controller of BBC1 turn out to be an Auton replica.
The story finished with a climactic struggle at the top of Big Ben.
Illegal Alien by Mike Tucker
1940, and London is in the grip of the Blitz. Private detective Cory McBride is more interested in his whisky bottle than a large metallic sphere that he discovers shortly before falling unconscious. He is later approached by the Doctor and Ace, who are curious about an article about his encounter which they read in ‘tomorrow’s’ newspaper.
They learn that London is being terrorized by a serial killer nicknamed the ‘Limehouse Lurker’, who squashes his victims like tomatoes. McBride gathers information from his underworld contacts, including George Limb, formerly of military intelligence.
The Doctor suspects that the Lurker is a time-travelling Cyberman, bombed by the Luftwaffe and now seeking blood plasma to heal its damaged organic components.