Luckily, doors are immune to thermite. The RCD can be used to take one apart for only ten units, though, so be wary. If you have a welder, energy sword, energy gun, or some other strong weapon/multiple people, you could also bash open the window in the escape airlock and then the shuttle, hopefully without dying to the void. Connecting oxygen first gives you a very good chance of making it in before going critical, but you'll probably be killed after you get on. Blowing up escape and the hallway leading to it after announcing your intentions could work. Make it unsafe for everyone without a suit to cross, kill everyone who dares. Not even the suicidally overconfident human wave of crewmen could beat the void. I think Bd managed to hijack the shuttle by blasting Metastation's escape off the map with a gargantuan uncapped bomb he built.
Also: Using a bomb to crack escape without a really, really good reason will most likely result in you being yelled at by the admins.
Well, breaking the window will only get you to the shuttle wall. You can't break those, right?
If you want to get into the shuttle without dismantling a door, you have to get in through space.
Let me clarify what I mean. I call the shuttle. When there's 5 minutes left until it arrives, I head over to escape, and cut the door bolt light, and door bolt wires on all but 1 of the external escape doors. Then I go out the last one, and seal that behind me, then I hang out in space until the shuttle gets there.
Once the shuttle arrives, I spacewalk my way to the top of it, then undo a window, resealing it behind me.
This leaves me in a fully sealed shuttle, and means to get to me the crew will need to A. Dismantle a door, or B. Suit up and do the same thing I did, except now there's someone with a gun while they try to get in through a one tile wide window.
Planting a bomb at escape to blow up the crew while they try to break into the shuttle would probably be overkill, but I might do it sometime for the evulz...
I could only imaging that if e-mags sent the shuttle right away again, this would be a virtually guaranteed shuttle steal.
Stealing the RCDs is sounding like a good idea before you start this process, then I guess you could throw some Rwalls up in front of the escape doors to foil the crew even more. Let the chemists think they're so cool while they thermite your Rwall, then laugh as they can't get through the airlock right behind it.
My point is that stealing the shuttle is not impossible, but you have to assume the crew is going to act like a bunch of lemmings trying to get onto that shuttle.
Although really, your plan as antag should never depend on the crew acting like rational human beings.