Mostly unexperienced and often speculating, I only can add some thoughts about this.
Personally I dislike the very idea of dative as "indirect object". Isn't this term only a description how this works, as looked at from a point of view of our native languages? Recently I found myself to think about dative case strictly from Na’vi viewpoint - as a "recipient of the action".
So, if I am looking at effects of reflexive and causative on "ditransitive" verbs, they are pretty clear and self explanatory:Reflexive
makes the subject
to be the object
as well.Oe ngaru täpìng
am giving myself
to you" - of course this is not practical in literal sense, seems to me like an idiom, but grammatically correct and clear.Causative
turns the "doing something" thing into "make someone to do something", and the important thing to notice is the fact, that it changes the verb - the core action is changed from "doing..." to "making...". Thus the dative case is the recipient of the action "making", not the one of the action "doing".
So, in Na’vi it is only ONE verb, while in Earth languages we have TWO verbs. This limits our ability to use dative case for both of this verbs, because we need to express TWO recipients - one for original verb and another for "make".
The construction *"Oel poru teykìsyìng tsat ngar.
" - "I WILL make him to give that to you." is incorrect at this time and surely requires a closer look of Karyu Pawl, because we need to replace one of the datives by something else, or to somehow limit the free word order by bonding <eyk>-corresponding-dative to the "oel".
My unofficial and unapproved approach is to use the topical: *"Ngari oel poru teykìsyìng tsat.
" - literally "As for you, I WILL make him to give that."