Belt was largely shielded from opposition left handers being deployed against him by the largely right handed makeup of the top of the Jays order. Unless there is another major acquisition of a quality left handed bat on top of a potential Pederson acquisition then this will continue to be the case. Belt faced left handed pitching in approximately 18% of his plate appearances compared to about 12% for guys like Vlad and Bo.
Pederson was actually a fair bit better than Belt's 2023 as recently as 2022. Belt was actually quite a bit worse than Pederson against left handed pitching last season and struggled to a similar degree in 2022 as well so Pederson's splits won't be of any more concern than they were for Belt. The team has plenty of right handed players already on the roster that can spend time at DH to platoon with Pederson such as Vlad, Kirk, Jansen, Springer and Schneider.
My only real issue with Pederson is how it skews the outfield as being overly left handed and there isn't really a good right handed outfielder on the roster to face tough righties in place of the likes of Kiermaier, Varsho and Pederson if he were acquired. The team largely employed Merrifield in that role with semi decent results, hopefully the plan isn't to use IKF in this type of role as well.