That sounds awesome, but I do have some small degree of reservation about this idea, because changes the fundamentals of great generals so much.
I don't know about anyone else, but I don't really get overly attached to my warlord units. Sure, it hurts when they die, but there will always be more of them later. That said, I usually just create a single warlord (a medic), to qualify for West Point, then settle all my other great generals. To me, it makes more sense to reap the benefits of a continuing +2 xp/unit bonus vs a one-time +20 xp bonus and a handful of warlord-only promotions.
The stack promotions might tempt me away from my current behavior, but those are some major changes to the promotion system. Again, I find the ideas to be intriguing, yet I'm reluctant to actually jump on that, because it changes the promotion system so fundamentally. All of a sudden, promotions can affect other units? That's huge. It would require extensive game-testing to prove to me that it's balanced.
All in all, I'm a coward. I shy away from mods that introduce sweeping changes, especially when multiple parts of the game are changed (promotions, great people, the tech tree, etc) all at once. If you guys implement all these great-sounding ideas, I'll cheer you on (and perhaps even contribute a piece of code or two), but it's unlikely that I'll actually use the mod. Really, it's no big loss. But I have to say that I got kind of excited when I saw a mod with such small scope (BUG + BULL + BBAI + Praetorian nerf), because I'd been meaning to do the exact same thing for years now. That's me... a lazy coward!
May I just say, Powerslave, that essentially you are one of the exact people this mod is aimed at.
I mentioned the criteria above, but basically this mod is sticking to the KISS principle (Keep it simple and stupid). I appreciate that a large number of suggestions have been made in this thread, but only a few have been looked at under a magnifying glass, and even those that were should probably stand for closer inspection.
For example, originally I increased the cost of the granary by 20
because I believed the granary to be the obvious choice first build far too often, and I wanted to increase the advantage of using alternative build orders. However, it was pointed out by one or two that the change did not really seem to have any interesting effect on gameplay in the end, as it didn't provide enough disincentive to
not build the granary first all the time. So one might be forgiven for thinking that the logical next step to take would be to increase the cost further. But I remember noting to myself when I increased the granary cost that it didn't seem very realistic at all and it felt like it was already pushing in terms of how substantial a change it was. It's my opinion that increasing its cost even further is likely to have consequences that are only going to be more negative on gameplay. And it was also pointed out that the granary was only powerful because of Slavery and that Slavery should be re-examined instead.
So after all that, I have committed to undoing the change made to the granary (it will be returned to normal in the next release) unless further arguments for the change were able to convince me again.
Now it would be worth mentioning that I am open to accept criticisms on any single change I have made so far or intend to make. This does not necessarily mean that when there is debate over a change, the decision will be made based on the majority belief, but more like what the easily intimidated want. It's not really in the same category as most other feature-based mods.
I'm tempted to call it a flat-out balance mod but I don't want to exclude the possibility of making some changes that might improve gameplay without specifically addressing any one balance concern.
The bigger the change suggested for the mod, the less likely I am to think it will be a good idea. For example, your suggestion, killmeplease, does not IMO answer adequately several of the criteria. Further explanation and justification may change my mind but at the moment, making a change that includes several smaller changes (changing it to a world wonder, making a new promotion, changing or removing the standard GG promotion, xp cost reduction, improving Combat 4 (quite significantly! and thus improving Agg leaders), etc.) is almost out of the question.