It wouldn't surprise me if ten Hag goes ahead and signs Timber. Timber is good on the ball but is also comfortable on either foot, as well being aggressive and explosive over the first few yards.
But for me the #1 left footed CB signing should be Josko Gvardiol. He's a rolls royce on the ball, both at passing and dribbling out of the defence. And also provides a aggressiveness that is missing, along with a turn of pace over the first few yards.
So what we need is a pair of CBs who provide a solid base in a high line if we're to transition into a team that has ambitions to play the game in the opponents half, which ten Hag wlll look to work towards. So the CBs in defensive transition will have to go body to body with the opposing attackers in a high line to maintain the squeeze on the opponent. But they'll also have to provide play making ability when the team is in possession, so for me Gvardiol would be the pick of the bunch. He's still very young but i'd personally be more excited if we signed him than Nkunku from RB Leipzig. And the reason I say that is due to my belief that the two CBs, two fullbacks and deeper midfielders, being of absolute paramount importance to a head coach who wants to work towards creating a proactive attacking team where everyone attacks and everyone defends with high tempo/high intensity. So the aforementioned positions create a platform/foundation for the forwards to then thrive in offensive transition and also effectively press high. And you can't effectively press high if the players behind you aren't strong in 'rest defence' which is to stay tight to the the opponent's most advanced attackers.