I think of it as more of a ‘demo piece’ myself, which is to say that it can have as many themes as it likes! Different themes for different levels as no coherence is really required - just cool stuff:-) Yes there was a plan for a Crysis-style sequence of levels, but we just don’t have the resources, so really just a list of demo levels will have to do.
The one restriction I do have to insist on is that content is ‘open’, i.e. under a creative commons style license and with original modelling files available in a free file format so people can go and look at and edit them - conditions that the Warzone stuff does not satisfy.
P.S. I know what typically causes that error - its objects escaping the level basically. I thought that had been dealt with, but I’m guessing not.