The type of functionality you're talking about has never been done, but someone DID do a "dynamic battles" mod that looks really sweet. Basically, the fighter AI was applied to most frigates and cruisers, causing a big, chaotic battle with everything moving all the time. Do a search for "Dynamic battle" on the boards, and it should show up.

My guess as to why this is a difficult thing to implement is that it would also heavily complicate the combat. Sins is a strategy focused game design, as opposed to tactically focused, and does generally try to stay away from game elements that require heavy micro-management to be any good with. The CPU requirements for doing so would also be quite immense (even after applying workarounds) since you're talking about a costly search that must be repeated often for each unit, and with a thousand ships flying about that adds up fast! I can think of workarounds and shortcuts, but even then the CPU hit would still be staggering.

You don't seem to understand the technical requirements of finding an optimal orientation to balance offense and defense. To do that accurately means taking every ship in weapons range and testing a wide variety of possible orientations/positions for ideal damage input and output. That is NOT a trivial search, even once optimization has been done. To repeat that for every ship on any kind of consistent basis would be a huge task for the CPU, since it would be an O(n^2) time search. That means that every time you double the number of ships involved, the CPU requirements quadruple. As you can well imagine, that doesn't scale well.

Multithreading just brings more processing power to bear, it doesn't change the fact that the algorithm would never scale well without resorting to a lot of dirty hacks or suboptimal tricks, which would probably defeat the purpose of the exercise. Really, it's a high cost feature that results in too little gain, especially when considered alongside simpler options for making combat look more interesting (see the mod I talked about, I just gave it a shot earlier this week and it is sweet!)

As for the original idea, I don't think it would be good in Sins. Soase already has a pretty wicked damage-calculation system. Ships sometimes blow up before the finishing salvo of missiles even reach them. Sometimes thy blow up 2 seconds after they are lethally hit. Finally, sometimes weapon animations do not show at all in order to save memory.

This wouldn't work. Considering this game is not commanded by one server but relies on the deterministic random number generator, I can already see the desyncs resulting from people turning their ships under fire.
One player will have the damage calculated as if that ship was facing sideways, other will have half of the damage calculated as if it was already facing to the attacker. Ship blows on this screen and does not on another. Desync.

I dunno.