It would be a shame if too many renders from that first day at college are changed, all for the sake of one hairdo. Honestly, I'd be fine if Ocean just "hung a lantern on it" - i.e. have Mila comment later that she was just trying a different hairstyle during those first few days. But, as you say, her body is different too... so, it's more than just the hairstyle. If he does revisit it, I hope Ocean can render those scenes exactly the same, but with an updated Mila.
I'd imagine he has the scenes backed up, and all he'd have to do is load the assets to rerender - that would be sensible anyway - always keeping a backup of the unflattened project file in case you lose the render.
Then it'd just be the simple case of tweaking Mila's assets. I might be naive, but that's how most multimedia stuff works, you have all the raw assets, a file stores how they interact together in the app space, and then you can churn out all your separate format outputs. I don't do graphic rendering, but the principle is probably the same as what I'm used to.
I saw this comment in reddit -> "Less than 200 line means update possible in maybe 3-4 months."
is this true ?
From the dev log a couple of pages back, down the bottom after the distracting Nami renders:
"Less than 200 lines are left. I can see the light.
It also feels so good to work on Season 2 again."
Someone replied then that we'd see it at the end of March as a usual trollish Ocean-can't-tie-his-shoes-without-tripping-over-a-render-pc kinda comment.
I think it means something like 200 lines of the script to connect to renders - ie the renders are all done, but need to be put into place and tested etc. I don't expect this will delay anything. The time sink items are the intro cinematic and the gallery.