Quoting Matthew McCall
While I love the first vehicle, I'm going to be honest with you, I don't really like the second vehicle. It seems, well, too long, and it looks strange to have the howitzer (which does look awesome by the way) in a "pit". Also, I'm pretty sure you don't want to mix howitzers with APCs, as neither ability really works with the other and would basically result in crippling the functionality of both. Sorry about that, perhaps it would be better to make it into two seperate vehicles?
While the howitzer vehicle is modeled after a real design which holds the gun in a "lowered" position, I don't believe the real one serves as an APC, so in retrospect, I agree with you, thank you for your comment.