Consider a situation whereby a speaker community reinterprets the argument structure of a verb depending on the person of the subject. An example where this might be reasonable to occur is various verbs for 'like' in a variety of languages:
I like → I like
you like → you like
he likes → he appeals to X
much like, say, 'es gefällt mir' structurally is something like 'it appeals to me', but is semantically probably closer to 'I like it'. It is easy to imagine that first and second person more often perceive the appeal, and third person are the cause thereof, and semantic wear turns the structure, rather than the verb, into the meaning-carrying element.
This could imaginably lead to an inverse-direct thing for verbs with such a behaviour. Another thing it imaginably could lead to would be an exceptional voice whereby the behaviour of the verb for first and second person is recreated for the third person as well.
This would differ from other voices in the language, since
- it is restricted with regards to person
- it does not demote anything
- it does not promote anything
- it only permits that a certain type of NP behave like another type of NP with regards to the verb
(Now, we can imagine that it doesn't even permit first and second person "objects" – i.e. with this voice, you still can't say 'she likes me'. This would be somewhat interesting, but let's not go there.)
A tiny challenge: what could naturally grammaticalize into this function?
Onwards with the idea, this could of course combine with a passive - since normally, the stimulus is the subject, we could now go for a situation where you first make the perceiver the subject, then passivize so the stimulus again is the subject - maybe in order to get rid of the perceiver altogether, for a meaning along the lines of 'X is appealing (in general)'.