more of insight into X-Com - Council relations.
I'll admit I'm not very far at all, but I thought up something this morning exactly along these lines:
The mod's all about red tape, but who is causing all that red tape? Why do you HAVE to eliminate at least one cult before you can research promotion III? Well what I figured is that the UN bureaucrats are effectively deadlocked due to cult interference prior to the elimination of at least one. With evidence to back up the corruption of a handful of certain UN officials, their non-cult allies distance themselves quickly and throw their support behind XCOM. So even if the other cults are around, the deadlock is ended and enough of a majority now exists for all restrictions to be jettisoned. Pretty simple explanation.
Would be nice if something along those lines unlocked along with Promotion I, II, and III. Partial text from a meeting or recorded phone call about why XCOM is being so heavily stonewalled, even if you drag a sectoid corpse right in front of them.