So which suggestions would you highlight to BW?
Okay, for instance: Don't give the player choices that aren't going to mean much. For example, the mage or elf boon in DA:O. That was presented as something that would have an impact on future games. Instead, due to understandable reasons, the devs handwaved in a reason. Which is fine, but I don't think it should have been offered in the first place if they weren't going to stick with it for any future game.
Either the DA devs didn't plan for a series very well, or they had planned on the reward not sticking. From what I was told from TW fans, their devs largely avoid that. If they can't follow through with a possible choice and do it well for the player for the next game, they just cut it out early. Before the game comes out early. I don't know if it's because TW was planned from the start as a set series of games.
So far, they also haven't allowed things like any possible writer changes have a deep impact on the story. An example I was given was the dropped dark energy plot from ME. It was built up quite heavily, yet completely left unmentioned in ME3 due to the person behind the idea leaving the company. Fans of TW have stated that so far CDPR doesn't allow things like that to happen. Not the writers possibly getting moved to other projects, but they haven't built up a rather significant part of the overall plot only to drop it in between games. So BioWare writers might want to work more as a group than as an individual in case they have a change of staff. That way certain plot elements like dark energy wouldn't be dropped so unceremoniously.
That's a couple of the suggestions I've read, and those I can agree with. 
The blood, sex, gore, ect ect is a case of personal taste and something I don't find as useful for me personally as suggestions like that one does. This is of course based on the previous two Witcher games, and not the third. That's just what I've been told so far.