I seem to have missed the meat of this discussion, but I'll come out in favor of giving the player the ability to work for an "optimal" solution.
In this case, I think of the Quarian/Geth conflict in Mass Effect 3 where if you put in the work, you can achieve peace (which is obviously the optimal solution).
When I play games like Mass Effect, I want to feel like the hero. Call it childish, call is sophmoric or whatever, but when I play games I generally want to feel good. I don't care if you have to make me work for that perfect solution. In fact, I generally prefer it if you really make me work hard in order to achieve something great. I don't want those perfect solutions gift-wrapped.
Mass Effect's problem with the P/R system is that it became lazy. They simply conditioned players to always pick top right or bottom right, depending on what they were doing. Honestly, what I'd like to have happen is mostly separate morality and dialogue choices. Make it so you have to have fulfilled earlier obligations in order to open up those extra dialogue. Again, think the Geth/Quarian final choice.
So, for instance, if you happened to help Person X and were sympathetic to them, when a later situation comes up that requires their assistance, the player would be given new options to arrive at an optimal solution.
Similarly, you can mix it to somewhat discourage just playing "Johnny Squarejaw" or whatever. Let's take a scenario where you encounter some villain character and are given the option of killing him or not. In that situation, the "wholesome" option is to let them live. However, later on, if he lived, he'll reappear in a crucial situation and prevent the optimal solution from being achieved.
Kind of like the whole Geth rewrite/destroy option.
I think I'd also be willing to have the occasional choice in which there is no perfect solution, but I'd rather it be the exception as opposed to the norm. For one thing, having them be rarer makes them stand out more. For instance, I still feel that the choice at the end of Bring Down the Sky is one of the hardest choices in the series, and that DLC remains most memorable to me because of that choice, and because that situation was relatively rare.
Basically, I want to be able to access a (near) perfect playthrough if I so wish, but I also want to be made to work for it, and I really think that's possible.
Bioware just needs to divorce an overall morality system from their dialogue, get away from training players to always respond in the same way regardless of how they really feel for fear of being penalized, and be willing to accept that some players are going to make decisions that will reward them less.
I have zero problem "penalizing" a player with suboptimal solutions if they're unwilling to put in the work to achieve perfect results.
I think there are places for series where everything is terrible and everything is all grey and whatnot. There's places for elements of that in Mass Effect, but on the whole the series is still a lot more aspirational than The Witcher, for instance.