thats why we write, to expand on each others' comments.
Indeed

effectively, I will have to do some more thinking into possible conditions, effects and so on. I would say a slowly declining one time effect would be nice from a dramatic point of view, but would be too complicated to keep track of. depending on counter measures, a stable effect that is valid as long the condition is present/ nothing is done against it, would probably best.
For that notion, one of the simplest effects could just be some small penalty for the fleet that got caught off guard. Perhaps, ships only do 90/95% damage, explained by the crew being unfocused/unprepared for the battle. But with that effect, the permanent penalty wouldn't make much sense. They get caught by surprise, but it shouldn't take very long to regain posture and focus on the task. Likewise, if the condition is triggered by an enemy fleet being 'behind', then it doesn't take long for ships to turn around, and the same effect should no longer trigger afterwards. And as far as counters for this, other than "know which way they're coming from", there probably wouldn't be any?
ah, silly me. I did think of those two examples, but then I forgot to incorporate them into my post. I agree, a temporal effect would make more sense in that situation. with the rest I agree, its along the lines of what I had in thought myself.
and again correct, counters would be a bit hard. one counter imaginable is, if a scout saw the whole or part of the fleet amassing in another grav well. then, the attack would not come as a surprise, but the fleet would be prepared. but the again, when defending you have psidar most of the time which give fleets a warning of incoming fleets thus mitigating the moral effect of any such effect. consequently, that example at least would be far more valid when applied to a neutral or enemy grav well.
hm, in retrospection I think I got the civic moral idea from the simple fact that in imperium galactica they had a happniness factor called morale that would limit the tax rate you could demand from your citizens. I also think that approach would be more workable, it would be really nice to have it linked to the military side of things, i.e. take developments and outcomes in the war into consideration as well as those civilian things happenening. (trade ports could also give a little extra bonus for the "we love our exotic goods" effect).
to follow up on that other notion, even though thats really off topic: if you actually do have a system influencing well influence/ culture, also some permanent ones, then you could include a variable tax rate. no, wait makes no sense the way things are now, increasing the taxe rate increases taxes, but lowers influence, so no effect. hm, gotta think of that too.
on the miliary side: you could also include specialised ships or abilities that improve morale or rather that eliminate bad morale if it is encountered. I don't particularly like it myself though. not sure I mentioned it, capships could also play that role, as they are literally the command centres and backbone of fleets. would make them even stronger than they are now though.
conditions: destruction or fleeing of a capship could have a morale impact. then again, you have the problem with making an already strong player even stronger and the loss of a capship is even dearer than it currently is. maybe destruction of a capship belonging to the larger fleet or better belonging to an attacking fleet could give a larger bonus to morale ( think of "hey, we took one o'em down, maybe we do stand a chance"). its possible to do that even when you're quite outnumbered.
lastly, there is yet another route to take on morale, which could be goverment or fleet organisation. basically what it comes down to is, that you have the possibility to choose among a few doctrines on what type of military you want to have, more professional, draft, how strict hierarchy would be. depending on the type you get different bonuses. in an extremely tight regime, you could have less morale effects and no desertations, as everyone who does get shot down by his own ( thinking of starship troopers here). on the downside, there might be negative effects on tax income or production rates. I don't think we will see something like this, too massive for the time remaining and I heard goverments would not be an issue. but it would be a trade where you accept the possibility of negative tactical modifiers in exchange for some benefit or another.