Well, it became to be a IFV more by chance. As I had so many versions of the box-like vehicle (e.g. flaketom.deviantart.com/art/Pr… ) I thought an IFV would be nice. So idea was that the boxy base vehicle was available in huge numbers and a need for an IFV came up, so they used these as base to create an IFV, that's also the reason of the troop compartment being in the turret. That also explains the kind of armour it has. Mostly add on and ERA armour.
It's not perfect and very reasonable, but as I wanted to do a boxy IFV out of my base vehicle that is what I came up with.