I don't necessarily think MVAM is a stupid idea. I understand the argument against but also think there are some fairly strong arguments for.
Firstly, it was designed to be piloted by minimal crew for the soul purpose of combat (it can be piloted by a mere 4 personnel if i remember correctly). Such a vessel would not require the perks and facilities of a mainline exploration starship (holodecks, science facilities etc.). Also, its high degree of automation also negates the need for a large crew. The less crew on board the less space and energy required to accommodate them.
Generally speaking the more opponents you face the lower your chance of victory. History dictates that if you are surrounded you are effectively stuffed (take any major European war from the Napoleonic to WW2). Having a ship that splits into 3 just gives you more options in a fight and options are always a bonus in a crisis.
I should imagine the extra surface area exposed after MVAM is initiated would be a bonus due to previously hidden phaser strips being exposed and added to the already formidable arsenal.
Either way, I will search for a more Prometheus/MVAM based thread to carry on sticking my ore in. In regards to the original post I should imagine grav plating could be fitted however you like, as long as 'Warning: Variable Gravity Area' signs were posted nearby. I can imagine the accidents now.