I think Hanji would like it.

Maybe not the first mission, but in the first arc for sure. It could set up for something good.

I don't think it should be the same threat level as the Colossal Titan, seeing as though the Colossal Titan is more than 50 meters tall and twenty meters is pretty much the same size as the door (Ok, probably not, but still). Plus there's another reason the Colossal Titan is more dangerous....If you read the manga then you know x)

Colossal Titan [I]did[/I] have to make way for the smaller titans and the armored titans, I'm sure he could have done more than just kick the door in xD