"Should" has a lot of different meanings that aren't distinguished in any language I know of. Here are the three I can pinpoint:
"False subject". This one is the vaguest, but here's an example: "Rey shouldn't have defeated Kylo in The Force Awakens". It's neither a moral nor a strategic should - at least, not one that applies to Rey. The statement it's actually making is that the story would be better if this didn't happen, in other words, Rey isn't the subject of the 'should'; the story or the writer is. Hence the name.
This is also used for jokes (X should have happened = it would've been funny if X had happened), general design (user interface consultant says "the button should be here" = "the interface is better if the button is here"), et cetera. The only consistent rule of this form seems to be that the grammatical subject is not the semantic subject.
Spem of course is going to separate all these. They're all used as combo verbs. Here they are so far:
rɑ- "should": not doing it is morally reprehensible. rɑi- "shouldn't": doing it is morally reprehensible. Basically this can be thought of as a convenience alias for rɑ nu. ri- The action is morally admirable, but not doing it is excusable.
I should move it. =
mi rɑ nɪv ɪl.
I shouldn't move it. =
mi rɑi nɪv ɪl.
I have to move it. =
mi tir rɑ nɪv ɪl.
Ideally, / if I were a really great person, I'd move it. =
mi ri nɪv ɪl.
There's no reason I should move it. =
mi nu rɑ nɪv ɪl.
(I should, but) I don't have to move it... (it wouldn't be that bad if I didn't...) =
mi nu tir rɑ nɪv ɪl...(eg: ideally one should sacrifice one's life in this situation, but can hardly be blamed for not doing so)
I'm not sure if I need to add one for "two-sided moral irrelevance".
zɑ- "should": doing it will promote the subject's goals zɑi- "shouldn't": doing it will undermine the subject's goals
My tentative plan for this is to have a single word