AzaToth, the thing you've got to keep in mind is that this is a Sci-fi tactical FPS, not City of Heroes!

Magical capes of jumping, shades of 1337ness, and suchlike, do not fit in with the established game universe (such that there is), or what the developers are trying to achieve (from what I can ascertain).
As to flying aliens, it would easily destroy what balance has been achieved so far - between the humans and aliens, and amongst the aliens themselves. Jetpacks would instantly become pretty much redundant, for one...
In any case, this isn't a democracy; the developers have said no, so we're not getting them. This is a Good Thing IMO.
There's always that "mod" option under the main menu, nei?
