I'd like it if somebody experimented with the ingredients of religions to see what does what.  I'd like them to perform the standard indoctrinational actions upon experimental groups of people (and a control group with no intentional changes, in case they screw something up consistently) with certain parts of the standard tales and rituals removed.  For example, how it would affect the strength of religious followers' convictions if they've only ever been taught a version of the Jesus tale in which Jesus does not appear to some people after having died and respawned (no fish pun intended).

To actually get the complicit participation of the thousands of people needed to run this experiment would be impossible, of course.  Alas, were it possible and not likely to be seen widely as objectionable due to the fact that those indoctrinating the others don't actually believe it, it would be able to provide great insight into which parts of whatever mythology is most effective to attack.

I suppose that in the real world we'll just have to read people's deconversion stories.