I think the mobility thing kind of depends on what the plan is and who else we buy. We have to presume we're going to move towards a more energetic style. But I don't think that means every player in the side needs to be the quickest player around, certain positions have less emphasis on that quality. You don't exactly see Modric or Kroos legging it around.
He should have the positional nouse to give himself the run on opposition counters. We don't need him bombing into the opposition box too often. Ultimately it shouldn't be all that frequent that a midfielder like him is completely exposed IF we get our structure right and he understands his job. His job really is to improve our buildup, work hard, occasionally offer a long shot threat.
It's hard to get every quality in one package, Neves can give a lot in lifting our passing level, but yes you can get a more all round option, probably. They come with their own risks like relatively unproven, or maybe their technical level isn't as good.
I guess the worry is we also have Maguire. Maybe that's a bit too much of a recovery problem down the spine. If it wasn't for that I wouldn't be worried at all.