None at all. If plywood is touching the ground that is support too but I really like and use my side doors quite a bit so I say go for the wrapped trim.This looks awesome. I started mine today and it is square as square can be. Took my time through everything and glued the joints and then screwed them togethr. Currently I have no back support but may add one yet. I went with 2x6 upper base.
I was going to wrap with plywood and then cut out the cabinet openings but I think I maybe wrap it with trim pieces to accommodate the doors that I will have in the front and both sides, with 2x4’s all around, I am going to use the open areas on the sides for door access. Do you see any issue with this plan?
Just check level on your floors it can surprise you.