'The marquis. Well, you know, to be honest, he seems a little bit dodgy to me.'
'Mm,' she agreed. 'He's a little bit dodgy in the same way that rats are a little bit covered in fur."
On the Chitauri: Having soldiers whose life is maintained by a space ship is a very cruel and Thanosy thing to do. For me, it provides some early characterisation for Thanos.
On the tesseract: The tesseract has only shown the ability to teleport things in and teleport things away, not teleport itself.
On the helicarrier: The thing was already damaged. If it had arrived at the NY battle and had a space whale fly through it, it would be a very bad day for NY.