Purpose in MNCL5

I think I found some more problems with MNCL5 and solved one of them before
I even realized it was a problem. Here it is, with some background first.

Originally, MNCL5 had a simple rule stating that omitted arguments (i.e. those
which are allowed grammatically but don't appear) are, if anything, indefinite
(Note that this is distinct from the implied subjects of non-verb forms). Next,
when I was figuring out how to express purpose in MNCL5, I came up with the
idea of using an adverbial complement clause containing a subjunctive verb, as
in:

Mas kor'yek gil Jonita zo elefantok vidus di.
1-AGT.PL run-IPF-PST CCI John-DIM-PAT.SG 3A-ADJ elephant-THM.SG see-
SUB SCT-ADV
"We were running so that Johnny could see the elephant."

For some of the cases where the complement clause shares a referent with
the matrix clause, I decided that a prospective aspect participle component
with a secondary predicate final would be used, as in:

Jonitak korek zo elefanto vid'vi.
John-DIM-AGT.SG run-PST 3A-ADJ elephant-GEN.SG see-PRO-ADV
"Johnny ran to see the elephant."

(In this example, the secondary predicate final -i is identical to the adverbial
final, and has been glossed the same, even though the semantics are different)

However, this leaves some cases where a referent is shared, but the clause
can't be replaced by a component (such as when it has too many arguments
or an adverbial phrase). I originally used a 3rd person pronoun, or maybe a
reflexive pronoun, in the complement clause for the shared referent, but later
decided it could be omitted in many cases, even though this would require the
omitted argument rule to be modified. Example:

Jona cuzek Tomok gil (zak) Marxa gebus livrok din.
John-PAT.SG choose.PST Tom-THM.SG CCI (3A-AGT.SG) Marsha-PAT.SG give-
SUB book-THM.SG SCT-SEC
"John chose Tom to give Marsha a book."

Note that -in (SEC) is used instead of -i (ADV), since the coreferenced
argument is Tomok, not Jona.

Recently, I realized that ambiguity could occur if an additional argument were
omitted [Assume that there's an adverbial phrase preventing the clause from
being replaced by a component].

Jona cuzek Tomok gil gebus livrok [tomorrow] din.
John-PAT.SG choose.PST Tom-THM.SG CCI give-SUB book-THM.SG
[tomorrow] SCT-SEC
"John chose Tom to give/be given a book tomorrow."

A couple things could be done: (a) restore the 3rd person pronoun or (b) use
an indefinite pronoun for the other omitted argument. But then I came up with
something I like better: use a relative clause instead of an adverbial clause.
This uses one word fewer than (a) or (b) and is actually more consistent with
the grammar. Example:

Jona cuzek Tomok yak gebus livrok [tomorrow] din.
John-PAT.SG choose.PST Tom-THM.SG REL-AGT.SG give-SUB book-THM.SG
[tomorrow] SCT-SEC
"John chose Tom to give a book tomorrow."

This also eliminates the need to modify the omitted argument rule!