Okay, I may have made a (small) breakthrough in improving AI fleet behaviour (in relation to the MaxOdds field). At first, I thought I'd found a disastrous problem that was going to cause me nightmares, but I may in fact have come up with a way to get desirable behaviour (!). (This is a little related to this topic, a little related to the one we were talking about in the Nova forum, and a little related to things which came up in the AotC thread, but I ended up posting it here.)
The original problem went something like this:
Missions are set up so that the initial system is filled with warships (Council warships, but that's not important). These warships are neither allied with nor hostile to my ship (which is at the centre of the system)
A further mission is set up so that a Xenophobic fleet jumps into the system. This fleet is smaller - the Council fleet exceeds its MaxOdds ratio.
What happens? The entire Xeno fleet targets me! There are any number of Council ships that are closer than me, but they ignore them (except for the Xeno ship that the Council ships target - that one's in trouble). Why aren't they just running away? Well, it's the same problem we had before with the MaxOdds field (which came up in the AotC thread). This is (roughly) the Xeno AI's decision-making process:
I've arrived in a system. I hate everything that's not allied to me. What's the nearest thing to me that I hate?
Aha! A Council ship! (I hate them.) Are there other Council ships here ? Hmm, it seems there are. Too many for my MaxOdds value, in fact! I'm not going to attack them
Instead of attacking them, I shall not run away though. Instead, I will continue with my default behaviour. Before I get to looking to see if there's a port I want to dock at here (there isn't, in fact, because I hate the owners of this port!), there are some Merchant ships here! But wait, the Merchant govt is allied with the Council! Therefore, they count as part of the Council fleet, so I can't attack them either.
But there is one other ship here. This ship isn't allied with anyone. (It's my ship!) Let's all attack that! (I'm sure that Council fleet will leave us in peace to do it )
Thus we find ourselves watching the unedifying sight of four ships getting blown to pieces while trying to get to me, ignoring the huge unfriendly fleet that's attacking them (until they actually get hit/targeted, that is - and then it's too late).
The very same thing would happen in default Nova should a Pirate fleet jump into a system with a Federation (for example) fleet which exceeded its MaxOdds. The Pirates won't dare attack the Feds, but they will go for the player (and the Feds will pick them off).
But there is a solution! If I change the inherent AI of my ship to be that of the Council (or any ally of the Council), the Xeno fleet will count me as being part of that govt's fleet too (for the purposes of MaxOdds). This means they won't attack me either, because (the AI now realises) attacking me would require engaging a superior fleet. At last we get the desired fleet behaviour: the Xeno fleet now has an, 'Oh, @Ł$%' reaction, and tries to hyper straight back out again (typically, half of them make it, fyi).
So, it's possible that this may also improve (to an extent) the behaviour of the alien fleet in ARPIA2. More generally, anyone would be advised to set this up to ensure sane behaviour from Xeno fleets with MaxOdds settings (and, as pirates should generally not be fight-to-the-death types, most Xeno governments should ideally have MaxOdds settings).
What you need to do is set an inherent (combat) AI for every ship in the game that the player can get. Where it used to be '-1', it can be set to some 'Trader' govt: one which no one hates except govts which are Xeno anyway, and which everyone else of significance can be allied to without causing problems. You could create a new govt just for the purpose, in fact.
Once you've done this, make sure the friendly (eg, Arpia) fleet is allied to that govt (which most unaffiliated ships should be given), and the Xeno fleet should either run away (because MaxOdds are exceeded) or fight everything equally (if they're not).
In summary: the solution to (some forms of) bad behaviour by AI Xeno ships is to set govt class alliances as broadly as possible - and have them affect the player ship too.
(One final note: going back to the original example, let's say I'm flying a ship with a different inherent (combat) AI - one that belongs to an enemy of the Council. Now I'm not part of the Council fleet again, so the Xeno fleet will come after me. This, however, becomes a moot point, since the Council fleet now also hates me, and I'll be dead before I can notice the odd AI behaviour. :))