A possible workaround if possible now that you can create your own crew models and clothing. is to make an invisible crew member (No texture) that is always standing at the gun.
Now instead of a rain-coat give him a rain-cover that goes over the gun.
So in essence this is the only clothing the crew member has that has a visible texture.
So hes always there but transparent, during normal weather but as soon as it rain's his clothing is switched out for the visible gun cover.
Would this be possible.
