The third Doctor is one of my favourite classic Doctors, and so I feel that he deserves a larger spot in the mod, besides his sonic screwdriver and his cloak, and bessie and his TARDIS exterior. Here are some features I'd love to see added:

1) The 3rd Doctor's TARDIS interior

The first image is a mock-up of what a 3rd Doctor interior could look like. It could probably use a new set of roundels, and a better build of the computer/fault locator at the back, and I know not everyone likes the console models, but I think it's better than any block-based model I could make at this time. The gold music stand at the back was made from the time machine light (you know the one) placed on the floor.

2) The Sontaran Scout Ships

The second and third images are that of this particular ship. It would spawn most likely in the overworld, and would spawn 1-2 sontarans with it. The inside is simple, and could probably use some work, but consists of a seat and a player locator panel. A door may be added, but I was trying to make it as small as possible. I used stone bricks (a new block set may be ideal), but I feel this works well. A variation on this could be one half-buried in the ground rather than flush with it. 

3) The Master

Not just a third Doctor feature, but the 4th image is the Delgado master, a mob/boss i would love to see in the mod. (if you'd like, he could appear as one his other incarnations if you used a spawn egg, or whenever it spawns naturally, the incarnation changes). The master's TARDIS could spawn naturally, and inside would be the master, and that's where you'd fight him. Maybe the devs would rather not have a TARDIS spawn naturally in the overworld, so that you still have to craft it. The boss would be challenging, so there would be work put in if you did just steal his TARDIS. He may drop the laser screwdriver, a TARDIS key, or maybe a tissue compression eliminator, which would be able to shrink mobs, similar to how the 2-Dis flattens them.

4) Nestene Asteroids

Similar to the previously removed Cyberman asteroids, this would be found randomly in the overworld. The nestene itself would be a mob, and would have the ability to spawn autons around it, until the player destroys it. It would probably drop plastic... I don't know what else. It could spawn in 3-5 parts, and autons would have an increased spawn point in the overworld while the nestene fragments are around. This way, it would have a larger impact on the world. (see pic. 6)

5) Omega

I'd love an Omega boss in the game. Maybe he could spawn on Gallifrey, in the citadel, or in a void like dimension with the antimatter. He'd be able to spawn gel guards to protect him, and would drop maybe his helmet, or maybe an elixir of life?

6) Spiridon Daleks

These daleks would be just like any other, but would be partially invisible. There'd still be an outline, but they'd be mostly transparent mobs. They would probably drop normal dalek things...

These are just my ideas, and I don't expect all of them to be implemented. Thanks for listening to me ramble!