re: the ai using different favor items. It's pretty easy to modify it so that the AI uses different favor items or randomly chooses between X number of favor items. That said, there is some reasoning behind having the AI almost always (if not always) choose blood of the fallen.
The most basic and logical reasoning is that blood of the fallen is by and large the most commonly used favor item period. Odds are that in any 3v3 human game, at least 5 people will have chosen blood of the fallen. Now, there are certain builds that benefit quite a bit by using blade of the serpent (spit ub or hybrid tb), but the AI usage is less than optimal. For instance, a big draw to a spit ub is in quickly destroying towers and having additional staying power. For the AI to use it the way a human would, the AI would have to run up to a tower while a creep wave is present, spit, then back off. Or take a little damage, spit, then back off. Then, cast BotS and repeat. Also adjust if humans are nearby. And those are just a few variables I can think of - there are more. Anyway, so the option is to train the AI to use a favor item like that optimally (knowing the AI will retreat anyway if its HP hits the retreat threshold) or give the AI an item that simply increases its HP and increases staying power that way.
Anyway, I personally think the best decision is to default the AI to using Blood of the Fallen. I'm not opposed to having the AI use other favor items, but I do believe its less than optimal almost 100% of the time vs blood.
Oh - and I do believe we tweaked some of the AI favor item usage logic, but don't remember for sure. Anyway, there's no harm at all in taking the mod as is and re-enabling some of the favor items and doing some testing on your own.