The Witcher 1 (Remake)

The first Witcher is an... interesting game

I think it has a unique atmosphere compared to the two sequels, much more... "earthy" I'd say in my language, don't know the right English word for that. The sequels are flashier and "grander", probably for the best, but still... wonder if they'll be able to capture that feeling in a remake.

Gameplay is the major barrier for the vast majority of people who try to play it, no doubt. I got used to it, but I would be 100% OK with it being replaced by a more modern, action-driven combat.

One thing I'd keep as close to the original as possible is the alchemy system, which I think is the best of the three games - in W2 you can only drink potions before combat, so you can't pop one potion "on the fly" and have to know which enemies you'll fight beforehand. W3 instead has you using Alcohol once you deplete a potion, which degrades the whole "collecting herbs" aspect of gameplay. W1 lets you use potions during fights AND requires you to find herbs with the right property for them.

The open-world.... I don't know how they'll manage to paint a tight-knit story onto an open-world "canvas". They'll inevitably have to change some stuff for the main story, add a TON of secondary quests (unless they want an empty open-world).

Story\character wise... well they'll have to address the elephant in the room: Geralt's amnesia and how nobody tells him about Ciri\Yennefer. The Witcher fandom for some reason blames Triss for this simply because she's the alternative romance choice for Geralt in the games, but conveniently forget how Vesemir doesn't tell anything to Geralt about at least Ciri (like, seriously, Uncle Vesemir?), or how Dandelion tells nothing either (you know, the bard who loves singing about Geralt, Yen, Ciri, their friends and their adventures).
The out-of-universe reason of course is that it's simply a plot-hole the writers for the game didn't want to deal with. And it was fine for a 2007 game, the first ever made by CDPR; but they'll need to add a good explanation for it now.
Also, they'll need to make adjustments to characters. Triss in the first game is kind of a mix between herself, Yennefer, Philippa Eilhart, they'll need to make her more similar to W2 and W3 Triss (without ruining her character development throughout the trilogy though).