Replacing the sprite is not complex. In fact we already have the new half-healed sprite working in-game. The programming itself was not too difficult, the biggest share of the work and difficulty was on dilukha's hands to make the new assets.
That said, there is some additional work involved because we decided to expand Asterion's range of emotions and that means that I have to go back to these earlier chapters and rescript a lot of content. Incidentally, this means that even if someone were to put the old files back in they would not really work, as the old spriteset will no longer have the assets to deliver all the new expressions.