Here's an insight: Every verb should take a direct object. Direct objects are the only type of information you can specify about a verb that doesn't require a preposition, so they're the fastest. Therefore, there shouldn't be any verbs that take indirect objects but no direct object. "Go" in English is an offender, because for some reason you have to say "go to somewhere" - why is the direct object slot unused? (Except for demonstratives and a few special nouns like "home".)

All Spem verbs of motion (and some other verbs) follow a pattern. The transitive one can be thought of as the "basic" one, since in theory it's sufficient without the other and the other is just a shortcut (which is not true in reverse). For example, nɪv is the most basic verb for expressing movement. It has the following syntax:

mover nɪv object previous location av new location

The av and clauses can be in either order. Any of the three object clauses can be omitted:

mi nɪv av djʌn = "I move stuff (unspecified stuff) over there".

You can actually leave them all three out: mi nɪv = "I move (unspecified stuff to an unspecified destination)" For comparison, in English you could say, "Don't move anything!" But the only reason English requires you to say "anything" is because "Don't move" would mean don't move yourself. In Spem transitive and reflexive versions of a verb are always separated, so you could just say "Don't move (stuff)" and have it distinguished from "Don't move (yourself)" by using nɪv versus vɪn.

The reason the object moved is the direct object of nɪv is because I think it's the mostly commonly specified. Another insight: Which object is which is theoretically arbitrary, but for the sake of speed, the most commonly-specified one should be the direct object.

The reflexive version of all Spem transitive verbs only exist as shortcuts. To continue the example, vɪn means "go" - to move oneself. Here's how you can convert any vɪn statement to a nɪv statement:

entity vɪn destination = (entity) nɪv entity av destination

I put the subject of nɪv in parentheses because it's not strictly implied - vɪn doesn't strictly mean the thing being moved is the thing doing the moving. For example, in English if you throw something and aren't sure where it went you could say "Where did it go?". You can also do this in Spem for any reflexive motion verb. Still, the implication of vɪn is useful because nɪv is usually used for being set in motion by something else, so nɪv mi without context would be understood as "I'm being moved".

Notice that that's the passive voice! In Spem, to get the passive voice you just leave the subject unspecified. I like this because it makes it obvious that the subject is missing and that there must be one. The passive voice in the way other languages implement it facilitates bad ideas because it allows you to omit the subject while still making it sound like a complete statement. For example: "it's known that..." or "it was discovered that..." or "A study was done..." Language like this can be used to discourage the listener from asking who knows it, who discovered it, who did the study; I've frequently seen this taken advantage of for dishonesty, by making it easy it to not realize that a crucial part of the claim is being omitted.