Narkissos....What about the pronominal shift? It doesn't rule out anything, but imho it would better support an interpretation in which the two are not identified.
Here is how Eric Meyers & Carol Meyers render the verse in their Anchor Bible version:
"Then I will pour out on the house of David and on the leaders of Jerusalem a spirit of favor and supplication, so that they will look to me concerning the one they have stabbed" (Zechariah 12:10; Anchor)
Here is what they write concerning the pronoun: "to me. The MT reading of 'elay, first-person singular, is supported in all the major versions. It is a reading, however, that ... seems to contradict the third-person references to the 'stabbed one' that follow in this verse. The most common emendation, therefore, is to change 'ly to the third person, 'lyw ('to him'), a reading that is supported by John 19:37 and Rev 1:7, where this text is quoted, and in a number of the Kennicott manuscripts...However, we find no reason to depart from the MT, which has overwhelming versional support. Indeed, the God-given change of disposition on the part of the traditional Jerusalem leadership certainly is consonant with the result of those people now looking to God as the source of their change of heart regarding what they have done." (p. 337)
And concerning 't 'shr, the authors comment: "As indicated in the preceding note, the interpretation of this phrase, 'et 'asher, cannot be separated from the reading of 'to me'. For the latter, our translation again reflects the MT. The accusative marker 'et indicates that the ensuing clause refers to the one who has fallen and is followed appropriately by the relative pronoun, which functions like a demonstrative, not unlike that in Mic 6:1 (GKC 138.e). The syntax is difficult, to be sure, and other translators would simply substitute 'because' for 'et 'asher, an approach adopted by the Targums and subsequent Jewish commentators, who see the nations turning to God because they were responsible for the martyrdom of the 'stabbed one'... Keeping 'to me' ('ly), which refers to Yahweh, and not emending, makes it difficult to understand the following 'et 'asher, because 'et is the sign of the direct object. The result would mean looking at both the one they stabbed and at Yahweh, who could not be the one stabbed ... with these two acts of looking being connected and with 'concerning' constituting a guess at how they are connected" (p. 337).
Another commentary (Baker Books series) by T. E. McComisky has this to say about 't 'shr: " 'shr alone can function as an object, but the addition of 't particularizes it, yielding 'him whom' or 'the one whom'. ... While it is permissible to understand 'shr as a causative particle, the Septuagint's translation [anth' hón ...] is suspect because it construes katórkhésanto without an object, a grammatical condition appropriate to the reading of the Masoretic Text (whom they pierced), but creating a somewhat awkward Greek rendering. The Septuagint thus witnesses to the unsuffixed verb in the Masoretic Text" (p. 1214). McComisky is thus less convinced of "concerning" or "because" as a rendering as opposed to the Meyers. McComisky also draws attention to the use of 't in Zechariah 7:7 in which 't occurs without a direct object.