The main verb tone or F-tone is a hypothetical new tone that would mark the main verb of a clause or sentence.
This would make 
purely a "post-determiner and serial-verb-making tone."
It is marked in this article with an "m above" diacritic. For example: Jaͫq chỏ jí ní sỉo da.
Introducing such a tone would have a few benefits:
- No more mandatory da or la fences between sentences, as this tone itself marks (the verb of) a new sentence. Dỉo da, nủaq da can just be Dıͫo, nuͫaq.
- It allows for coordinating clauses without a need for na, for example: gî ní na ru jỏe súq → gî ní ru joͫe súq.
- The falling tone becomes less common.
- It works nicely in the syntax: this tone is the "F" head of an "FP" (hence its second name).
The cost, of course, is "one more tone". It would be balanced out by merging adverbial tones (see Full Arguments).
Proposed reallocation
In August 2022 Hoemaı proposed a reallocation of the tones that includes a main verb tone.
https://discord.com/channels/311223912044167168/311223912044167168/1010869237331546162
In summary:
- Adverbials get
. - Variables get
(as before). - Serial tails get (as before).
- Relative clauses get
. - Main verbs get
, with 
as an optional allotone. - Content clauses get
or 
(they can merge to a single creaky tone).