Ahh ok that will definitely slow things down if he's redoing all the renders, but yeah at least he doesn't have to reinvent the wheel. He's already got most of his story laid out as well as the code so progress should still be faster initially. He should be able to just copy paste a lot of his events and then only have to do minor tweaks to them if he's changing mechanics or something.
Entirely new scenes will still be slower though. If I remember right, he uses a lot of layers and sprites for his renders so he can still reuse some of his renders even if he's using different character models. The clothing for instance is rendered separately if I'm not mistaken. So changing the character model doesn't matter for the clothing as long as it's close enough that the clothing layered on top looks like it fits.
Entirely new scenes will still be slower though. If I remember right, he uses a lot of layers and sprites for his renders so he can still reuse some of his renders even if he's using different character models. The clothing for instance is rendered separately if I'm not mistaken. So changing the character model doesn't matter for the clothing as long as it's close enough that the clothing layered on top looks like it fits.