Well, even just re-rendering would take quite a lot of time, plus there'd be bad lighting and other issues. So it'd be a half-measure and wouldn't add much to the game. I decided to go full, heh.I appreciate the work that goes into remaking the previous chapters and the comparisons make it clear this is a true remake. Characters are in different poses and wearing different outfits. Why not go the easy route and just re-render using higher render settings or better lighting?
And it's not about higher settings and number of iterations only, you need to tweak a lot of other parameters as well.
Easy example: a render with bad textures, lighting, expressions and so on will be equally bad at 100 and 15k iterations. The latter example just won't have noise/grain effect