maybe he has another level in him (like how dembele transformed back last season for spurs into the rampaging force that impressed at fulham) - but witsel the past few years is exactly the type of player who just sits back and maintains possession. a controller, great for tempo and defensive security, but not going to do those things you say (unless koeman works his magic perhaps)
Whenever I've seen him play for Belgium yes mate he does as you describe.
However, at club level (and on occasions at intl level (Euros vs ROI perfect example) he is the type of box to box player we need.
@bluestevon will be able to tell you more, but when I've watched him in the CL for Zenit he is the one making those runs from deep, using his strength and good footwork to protect the ball (he isn't particularly quick whereas Dembele has a burst of acceleration), but can also sit and dictate the play. You put him in a three-man midfield with a sitter to break up the play but who can also pick a pass, plus Barkley, I think you're onto a winner, especially if we can get a playmaker for one of the wing slots.