He could but he's better than our CBs and would likely cost too much to want to put him at rightback. He can dribble and get forward from CB but if we compare him to fullbacks he's not likely to have end product the way they are expected to these days
As a CB he'd improve us but I doubt we'd have as good a defensive record as Sevilla just by signing him. He's not VVD or something like that. But I dont think there are any of those available. I think at best he'd have an impact like Thiago Silva at Chelsea which is still good but not quite as good as VVD coming in. I think if Chelsea had Rudiger, Kounde and Chalobah they'd have a similar or slightly better defensive record than now with them still being behind City and Liverpool in that regard
Edit - I'll also throw this one out there just to see how good this suggestion looks in a couple of years time as they mature. But last summer I was 100% on wanting us to sign Romero. He's gone to Spurs and has had some good games, but also missed plenty of games.
Before that Kounde would have been my pick and now that he's no longer available I'd go with Kounde again. However, ideally I would have been most impressed with us signing both of them and having Romero and Kounde together in the next couple of years. I think that would be a partnership that could compete with Liverpool and City for the best defence. So lets see in a couple of years if Romero and Kounde seems like it would have been a great duo, or if I'm wrong and one or both dont end up among the better CBs around.