Hi there, I'm playing on Mighty Hero difficulty and I've got to the 7th Mission - Retrieving Date from Chaos ship. However, I forgot to take a techmarine! The mission states: "Techmarine must access the data terminal and retrieve its vital information. Guard the Techmarine at all costs." I've cleared the level but now I'm stuck. Have I lost the save due to my stupidity? Any help would be much appreciate, thanks!

No real help that I have to offer but I do think this is interesting. I didnt think they allowed you to even launch without the appropriate setup.

Anyway, complete shot in the dark, maybe one of the other units can activate the punch button at the end? I recall there was a way to abuse this as well and have the tech marine fully level up by endlessly pushing the button as they get XP every success.

Short answer : you're screwed ^^' !

Now, more in details, the way this particular mission is setup in the editor requires a Techmarine (and no other unit) to activate the terminal. And unlike the fith mission, for example, which featured an alternative (you could desactivate the power generators for the terminal... or just destroy them, one by one, until the whole power grid shut down), there's no such method here. I just checked with the editor, but no dice...
I'm a bit surprised, like Muttly, that you were able to launch the mission without selecting a Techmarine though. But, yes, the game isn't very constraining, so I guess this situation is possible... and awful in Mighty Hero mode, since you probably didn't keep a seperate file for every mission ^^'.

For your next playthroughts - and, yes, I sympathize for your loss, since it takes quite some investment to win in this mode ^^' -, I highly suggest that you take the time, in between missions, to make a copy of your save game file. This way, in case of emergency, you'll still be able to restart that mission.
I'm affraid I can't do more...