Looking very interesting so far.
Something to consider is that with the engine in the front, the drive sprockets need to be in the front as well. The power pack is a combined engine transmission and you don't want a drive shaft running though the crew compartment if you don't have to.
A total of 13 passengers is quite large for an APC so your idea that the side height might be a bit tall are not out of line. "in real life" (tm) with the extra width of the hull, the plan might be to sit the passengers a bit lower and drop the side wall height. Just a thought.
Also note that by running the armoured walls upwards from the hull sides and not extending them outward from the edge of the fender line, as the M113 and most APCs do, you are forgoing a lot of interior volume that the crew might really need. Now, a good use of the exterior wall space might be for both external stowage boxes, providing shaped charge stand-off distance, and as external armoured fuel tanks which also provide HEAT stand-off and get the fuel out of the passenger compartment maximising passenger numbers.
Just some thoughts.
Looking forward to this.
Paul