+1 I WANT THIS! The super heavy nose would make fighter operations very tough but what a great tool for buff hunting and tank busting!
Beer 
The gun mechanism and ammo is in the front of the bomb bay. It does not unbalance the plane at all. It will be a slightly heavier VI in term of performance. Slightly is a relative term of course for a large fighter to begin with. Mossie XVIII met LW planes numerous times and fought quite well.