I love this thread, so many great ideas going on about how to deal with this problem of seeing the RS and OS as separate POVS, especially "when everything is so blended together." I'm primarily a playwright and I do struggle with identifying and separating these two throughlines in at least my own mind so I'm clear on them, and yes I find it's messiest in two-handers. But this thread is helping, so here's a shot.
There aren't a lot of two-hander plays that are widely known, but if any of you are isolated now with a partner, family, or roommates, you've pretty much got the makings of a kitchen-sink single location stageplay - and if it's just two of you alone in a house or apartment, then that's a two-hander. So maybe think of that as an example. The OS between the two of you might be simply to survive this together - or to survive each other if things are a little more volatile between you. Or maybe the OS is to renovate the bathroom while under quarantine. Or to keep things normal, or to stay on track with work and finances as you both are working from home the whole time.
Let's say this is a very straightforward naturalistic play - by which I mean there's no theatrical memory scenes of the way they were, no internal monologues, no strange interlude alternate reality scenes, or scenes that break away from the main action of renovating that bathroom so that the couple can talk about their relationship or play cards as a break in clearly designated RS scenes. All the RS story points are going to be tangled up within the other three throughlines in every scene.
I'm loving @Greg's way of talking about the relationship as, like a character, wanting something, so I'm going as in his RS Being example: "It wants to pull lovers closer together, much like the earth and the moon are being pulled together by gravity."
I'm also loving @mlucas's RS graph charting that sort of togetherness, so I'm going to also assume that no matter what the players are doing in the OS, MC, and IC, that the RS is going to be nearly constantly in play, and the drama of the RS can be seen as charting its desire to be together as Mike has done. If two people who care about it each other - either in tenderness or hostility - are renovating a bathroom together, every hammer swing they do in the same room is going to pursue the OS objective, but the way the RS perceives the relationship is going to be operating at every moment. So maybe call that the subtext between them, or call it two perspectives operating at once, or call it two parallel universes operating in the same space.
And I'm going to suggest this isn't just the OS having a Cause and Effect on the RS. I'm going to suggest it's the RS doing it all on it's own - moving closer or farther from its desire of togetherness - and that the OS is just the context. The RS would be playing the same sort of drama of together/apart over breakfast, while robbing a bank, or trying to solve a murder in Chinatown.
Is this couple kind to each other while swinging a wrecking bar in that confined space? Judging each other's ability with the caulking gun? Considerate when maneuvering drywall into place on the ceiling? Irritated? Compassionate? Vengeful? Hanging on by a thread? Removing the clawfoot tub might be a complete success from the OS POV, but in that same space the RS has moved from positive (togetherness) to double negative (the edge of "I'm out of here").
Multiply by 4 acts, etc, and that's a two hander, or the really complicated overlapping of OS and RS in the four-hander Whose Afraid of Virginia Woolf, or Luke and Obi-Wan's relationship growing and shrinking and growing again while fighting the empire.
It seems to me that's a less abstract way of thinking of the RS as a character while keeping it tightly interwoven with the other throughlines - or am I just shuffling the deckchairs?