Well, there are a number of issues here.
(1) The idea that neuter gender necessitates non-person hood.
(2) The (apparent) idea that the pronoun must have a clause internal referent.
(3) The desire to make constructio ad sensum
the necessary explanation.
(1) The neuter gender does not imply a non-living referent. Neuters maybe used to refer to people.
Heb 7:7 wrote:χωρὶς δὲ πάσης ἀντιλογίας τὸ ἔλαττον ὑπὸ τοῦ κρείττονος εὐλογεῖται.
And without doubt the lesser [Abraham] is blessed by the greater [Melchizedek].
Dem., 8.41 (BDF §138(1)) wrote:ἥξει πάντα τὰ νῦν συμβεβιασμένα καὶ καταφεύξεται πρὸς ὑμᾶς·
Everyone now held back will be drawn to your side.
To assume the neuter necessitates non-personhood is the same mistake others have made to assume that masculine gender necessitates male-ness. This is particularly clear with substantive adjectives, which do not agree in gender with another referent, but also do not have lexically specified gender. Thus, they are the closest we can get in Greek to the "basic" meaning of the masculine, feminine and neuter.
Masculine gender marks a positive reference to personhood, but this person may be male of female.
Rev 22:11 wrote:ὁ ἀδικῶν ἀδικησάτω ἔτι καὶ ὁ ῥυπαρὸς ῥυπανθήτω ἔτι, καὶ ὁ δίκαιος δικαιοσύνην ποιησάτω ἔτι καὶ ὁ ἅγιος ἁγιασθήτω ἔτι.
Let the one who does wrong continue to do wrong; let the vile person continue to be vile; let the one who does right continue to do right; and let the holy person continue to be holy (NIV)
However, feminine substantive adjectives and participles are always female.
Thus we actually find the following distribution for the referents of gender categories:
(Mussies, Morphology of Koine Greek
(2) Your proposal/argument appears to make the assumption that the pronoun needs a clause internal referent. But this isn't the case. Bateman's view is entirely based on that assumption. That is "what was from the beginning, what we saw and heard, what we saw with out own eyes..." involves an entire event, not merely a individual entity (whether personal or not). There's nothing inherently wrong with this. The author of Ephesians does the same thing:
Eph 2:8 wrote:Τῇ γὰρ χάριτί ἐστε σεσῳσμένοι διὰ πίστεως· καὶ τοῦτο οὐκ ἐξ ὑμῶν, θεοῦ τὸ δῶρον·
For by grace you are saved through faith. And this is not yourselves, but a gift from God.
Here the neuter τοῦτο subsumes the entirety of the previous predication. It does not refer specifically to grace (feminine), salvation (masculine), or faith (feminine).
The phenomenon is also the motivation behind fixed expressions like διὰ τοῦτο "because of this," where the neuter refers to the previous piece of discourse. If we're assuming that introduction of 1 John refers to John's Gospel, then to the extent that "what we have heard and seen" is that Gospel, then Bateman's view is perfectly adequate and reads nothing more into the text than what you have already assumed. But let's not get ahead of ourselves. As I said, previously, I'm not entirely convinced by Bateman's proposal. I'm just saying it isn't as half-baked as you want it to be. On a (partially) related note, BDF states:
BDF §131 wrote:131. In adjectival or pronominal predicate. When the predicate stands for the subject conceived as a class and in the abstract, not as an individual instance or example, then classical usage puts the adjectival predicate in the neuter sing., even with subjects of another gender.
To the extent that we have a number of accusative neuter pronouns with no clear agreeing referent, it is relatively reasonable to accept that the intended referent could
be a broader more abstract event.
(3) Your appeal to constructio ad sensum
, I find rather unusual. I'm not sure that I've ever seen a discussion of the phenomenon with reference to a non-living entity with lexical non-neuter gender being referred to with a neuter pronoun. I've seen numerous cases of the opposite: a lexically neuter entity being referred to with either masculine or feminine gender. Maybe its possible, but it strikes me as odd. Winer-Moulton says as much as this:
Winer-Moulton 1882, 176 wrote:The gender of pronouns,—personal, demonstrative, and relative,—is not unfrequently different from that of the noun to which they refer, the meaning of the noun being considered rather than its grammatical gender (constructio ad sensum). This construction is most common when an animate object is denoted by a neuter substantive or a feminine abstract, in which case the masculine or feminine pronoun is used, according to the sex of the object.
I also cannot find anything in BDF that would suggest such an alternation.
Beyond that, there is still an alternative explanation for the gender of the pronouns that doesn't rely on constructio ad sensum
. However, to accept it, you'll have to give up the idea that neuter gender has anything to do with a lack of personhood. It's rather simple: sometime forward pointing pronouns take neuter gender (not always) simply because their at the point of speaker/writing their referent hasn't been stated yet. Consider the following:
2 Cor 13:9 wrote: χαίρομεν γὰρ ὅταν ἡμεῖς ἀσθενῶμεν, ὑμεῖς δὲ δυνατοὶ ἦτε· τοῦτο καὶ εὐχόμεθα, τὴν ὑμῶν κατάρτισιν.
e are glad whenever we are weak but you are strong; and our prayer is that you may be fully restored.
Rom 2:3 wrote:λογίζῃ δὲ τοῦτο, ὦ ἄνθρωπε ὁ κρίνων τοὺς τὰ τοιαῦτα πράσσοντας καὶ ποιῶν αὐτά, ὅτι σὺ ἐκφεύξῃ τὸ κρίμα τοῦ θεοῦ;
do you suppose this, O man, when you pass judgment on those who practice such things and do the same yourself, that you will escape the judgment of God?
Though it should probably be mentioned that examples like Rom 2:3 are the most common, where the neuter refers to a complement ὅτι clause, but even then, I think the concept is rather clear, since as we noted earlier, the neuter is used with reference to broader more abstract events. Speaking of which, here's one of those with a forward pointing neuter:
Luke 12:18 wrote:τοῦτο ποιήσω, καθελῶ μου τὰς ἀποθήκας καὶ μείζονας οἰκοδομήσω καὶ συνάξω ἐκεῖ πάντα τὸν σῖτον καὶ τὰ ἀγαθά μου
This is what I’ll do. I will tear down my barns and build bigger ones, and there I will store my surplus grain.
I would suggest that the neuter relative that we have here in 1 John functions similarly. And it explains well, why John then switches to the feminine pronoun ἥτις in verse 2