I would still prefer to wait till Bauckham discusses the inscription himself, and in particular to respond to Rollston's persuasive argument that the first letter of line 2 is either a zeta or tau but definitely not an iota. I would also like to see an epigrapher show other examples of iotas written that way.
If the word is not a representation of the Tetragrammaton, are there other likely candidates for what it could mean?
As mentioned above, Rollston has noticed that ]TA on line two and OC[ at the end of line one spell OCTA, i.e. osta "bones (plural)". The rest of the message is difficult to read because of uncertainty in reading some of the letters and because of the common use of abbreviations in ossuaries, and Rollston doesn't hazard further guesses.
It might be worthwhile to compare the potential readings against the existing corpus of ossuary inscriptional texts. Pau Figueras in Decorated Jewish Ossuaries (1983) mentions one ossuary inscription identifying the bones contained in the box as "Bones of those of (personal name)", i.e. OCTA TΩN TOU <personal name> (p. 13), so one might expect the text that follows OCTA to pertain to the name, nickname, profession, or other identity of the deceased. Another example of this: EΞΩKIZΩNTON OCTA... (BH)Θ IZATΩN "Bones of immigrants, Izatus family" (p. 15). Or less plausibly OCTA could pertain to a resurrection hope for the bones. Figueras (p. 14) mentions the lengthy Latin epitaph on the tomb of a Jewish woman Regina that proclaims "Let her rise up into the promised age" (surgat in aevum promissum), and the UΨΩ used in connection with the hypothetical OCTA and AΓIΩ in this inscription might have some connection with a resurrection belief, although hupsò does not seem to be used in connection with bones per se in resurrection texts (there are no hits in TLG re osta/ostea used in the same sentence with forms of hupsò), though it would make sense in connection with the lifting of bones out of the ossuary. Figueras notes that inscriptions like that of Regina are not likely to occur in ossuaries "knowing the usual brevity of language on ossuaries and the almost absolute absence of an open resurrection belief on the old Jewish epigraphy on tombs" (p. 14). The ΔI preceding OCTA could maybe be interpreted as a form of dia (shortened to di' when preceding a noun with an initial vowel), or it could also be an abbreviation of a word starting with di(. One possibility is didumos "twin", a word attested on ossuaries of twin brothers (p. 15), ΔI(ΔΥMΩN) OCTA for instance would be "bones of twins", but I don't know if that kind of shortening is attested in the corpus. Following OCTA is a sequence IO or IOU. This too could be an abbreviation of a Hebrew name; Figueras mentions IOU on one ossuary as an abbreviation of IOU(ΔA) "Judas" (p. 14). IO( if it is an abbreviation might shorten IΩ- names like IΩCHC (in the Goliath family ossuaries IOEZPOC is interchangeable with IΩEZPOC "Jehoezer"). Hachlili (Jewish Funerary Customs, Practices and Rites in the Second Temple Period, 2005) mentions that nicknames and abbreviated nicknames were common in ossuary inscriptions (pp. 232-233), which makes me wonder if an abbreviated nickname could lie in IOUΨΩAΓB (???), or whatever the actual text is.
Anyway these appear to be some extremely speculative possibilities by a layperson....the whole thing seems really uncertain to me without better readings of the inscription by experts, and the ossuary is not available for direct examination. I think it's too early to be certain on what the inscription says.