M Z LQY
"Bohan worshiped Set, the one who [would] stab you who [would] ruin this."
(this might be a slightly better version of what's below)
Ok so the first postulate was this:
M? Z LQ?Y
Who? this smites
Whoever smashes this, may Set stab you, the one who is celebrated by these [letters?].
But basically, the leftmost lines seem highly cluttered... why would someone do that and then widely space out the rightmost ones - the rightmost one, which also curves inward toward the right... Set's name (if accepted thus) is sort of dead center, slightly too far to the left maybe. So perhaps there was a stylized spacing, around that name, which does arguably have that effect anyway.
I've struggled with what that weird line (L???) to the left of the T_ is and it might just be a text directional indicator - which also wouldn't be totally unique (even at Wadi el-Hol I think it's pretty clear that a line groups three characters in the Horizontal Inscription into a cogent word (NFS2)). But the other problem is that given my above suggestion, which I pretty much held in reversing the column-order, why would the author use (B)HN, in this context which would have to unarguably be some type of plural pronoun, and then also Z an inarguable (at least in Hebrew) singular pronoun?
M Z LQY
So this led me to rethink the possibilities. There's a philological basis to this as well. I think the last(/first) two lines are very strong in that regard - M Z LQY / DcS.=K... "Whosoever this [should] efface(/break) / (Set) [will] stab you..." Granted this language is possibly unique, and maybe a little odd, but the formula is widespread among at least Arabian inscriptions - if you break this, you'll be blinded, a curse upon you, etc.
However... an inscription solely in that formula is pretty odd - why would someone write down ... if you ruin this you'll be ruined? That seems like a vain pursuit for the possibility of someone encountering it randomly - let alone being able to read it. More likely, that is the beginning or end of a dedicatory text. So whereas with the possible exception of S1T_, it's hard to finagle anything else except BHN. S1T_ - particularly in that orthography occurs at least tentatively in Thebes 6 (though not otherwise, and not Thebes 4). I cannot make anything of it besides Set (unless it's an improperly written phonetic loan from a dialect like Aramaic where they where it merged with T); but I'm open to suggestions.
I failed to mention that along with Thebes 6, this is the earliest non-Canaanite inscriptions (though these may predate almost all of that anyway) to use the Phoenician-form H. Along with the language present in Thebes 6, I think it's reasonable to assume that this is probably Syrian or Northern Canaanite and not actually Arabian - those similarities being the result of a dearth of evidence from the period, in part. However, I don't think one can make a clear claim that this is specifically Hebrew - and I am not knowledgeable enough in Aramaic to make that claim.
The really remarkable thing, though isn't that so much as what one comes to when investigating BHN. It's a plural of BN in South Arabian, but if we're sticking to the Ugaritic-Hebrew (essentially) clave or phylum, then Ugaritic offers no real help and Hebrew offers only two uses in the Bible (that are not pronominal): bohen "thumb" (Ex 29:20, Lev 8:23-4, 14:14, :17, :25, :28) and Bohan, apparently a son of Reuben (Joshua 15:6, 18:17).
When we re-parse the grammar - particularly noting the thought that this is dedicatory, it comes down to the first word (if the correct starting column) almost certainly being a name. This, or L (maybe M or B) would be the most obvious beginnings of dedicatory inscriptions. Moreover the presence of the name Bohan suggests this might have been a name otherwise. As for the unusual verbal treatment of H.G (expected H.GG), I have to assume this is the result of maybe gemination - which occurs at least in Aramaic.
In the Bible, H.G is almost exclusively used as 'feast' except in Psalms 118:27, where it seems to be used as 'sacrifice' and in Job 26:10 where it is the verbal 'to compass'. It's interesting, the Aramaic milieu is clearly 'celebrate' and the Hebrew is of a 'feast.' Murtonen (1990) stresses the broad continuity of the verbal use of to celebrate a feast, and I can't find a reason to really forego that. However, it's worth noting that it is difficult to differentiate between the continuum of shared vocabulary from Aramaic and very archaic Hebrew in this context.
M Z LQY
"Bohan celebrated a feast [for] Seth, the one who stabs you who [would] ruin this."
* Isaiah 42:24/Psalms 74:2
** This usage is odd but not impossible.