Render passes for compositing

UE4 can render images of a really good quality and because of this I want to extract render passes to do some compositing in an external software (like Nuke).
Both the sequencer editor and the high res screenshot tool give the opportunity to save some passes but there are some very important ones that are missing, like reflection, refraction and alpha.
Is there a possibility to extract those passes? Are there some tricks to use one of the existing to do the job? or maybe due to the nature of the engine is impossible to extract those passes?
I am really looking forward to find a solution because it would be a very good opportunity to have a very fast and high quality render engine.

Thank you!

God please someone enswer this…

Some passes(namely those, that are stored in gBuffer) can be extract using a simple post process materials, however they are of pretty low value for compositing.
To mimic other passes, you would need quite a few engine modifications done.