Hmm to make sure a vehicle isn't vulnerable against grenades. Well I don't know how good this idea is against molotovs I remember reading about what the British did with their Saracen armoured cars while in Ireland. They put a steal mesh/bars of some kind to protect it against RPGs but I could imagine you could fashion something similar like a little cage to prevent grenades from getting thrown in.

__________________
I have a new site for my table top tactical strategy role playing game for action figures and miniatures. There's also diostories there too! Check it out at: http://thewayofwar.net/