That's interesting. I was trying to think if these two optimism axes had some dependence on other variables.
I rather suspect they do, and that such an interaction is not just limited to the optimism axis.
My gut instinct is that reducing personality to a multiaxial classification is flawed, and it would be better to consider one's personality - or rather, the complex between personality and behaviour - as being more akin to an ecosystem in a stable equilibrium.
So modifying one small element of any of those may have much wider and potentially deeper effects. These might be helpful or catastrophic. Or it might do nothing at all, if the personality construct can absorb the changes.
I sometimes compare the whole personality/behaviour/mind complex as being like a giant wobbly meccano set. Nudge it lightly and nothing happens. Nudge it harder and it might wobble and then rebalance. Or it might collapse. Or it you nudge the right bit just the right amount, it might result in a sturdier, more stable structure developing. All those metaphorical outcomes have psychological correlates.
To return to, say, the OCEAN classification, I would suggest that yes, all those axes are to some extent interdependent, as OCEAN is a vast oversimplification of what's actually going on. Now, for most people, most of the time, it's not a bad first approximation, so the interdependence doesn't really matter for what it sets out to do.
One thing I've noticed is that idealistic people tend to be more acutely aware of negative things in the world.
I can't think of any existing research into this off the top of my head, but I wouldn't be surprised. I have previously thought that those on the right wing of the political are generally more optimistic than average and those of the left are by nature slightly pessimistic. This is contrary to most accepted wisdom on this issue, but I personally think it holds true, and is actually echoed by your postulated link between idealism and pessimism.
Interestingly, some studies demonstrate an effect of depressive hyperrealism, which shows that most of us, if not depressed, actually look through the world with slightly rose-tinted spectacles rather than assessing probabilities truly accurately. It doesn't take a shrink to guess why this might be a helpful trait, both on a personal and evolutionary level.
And since you mentioned OCEAN, I think we should all do that and post our results...
Openness to Experience = 57 ; Conscientiousness = 53 ; Extraversion = 43 ; Agreeableness = 43 ; Natural Reactions = 30.
Well, go on then: O59, C86, E15, A8, N5
That's just using a random online test, because I can't remember what I got when I last did it properly. I think it was the same sort of ballpark though.
I think the generous interpretation of my scores would be: "generally happy to listen to you and will consider what you say carefully but I really don't suffer fools gladly; not that you'll know that unless I want you to".
I will leave the not-so-generous interpretation to others...
