As a Dane, and fan of the club who sold him to Ajax, I would absolutely love it.
I can't put that bias aside, but if I try, I still see this as a sensible option. We would be getting a very clever player with great technical ability.
He's still a hard working player, but I expect that part of his game to become less prominent as he is getting older.
Still it a very good opportunity to get someone in for free, who is more than proven in the league. If we were to buy a player of his quality from another PL club, it would easily cost us 30-50m.