Which map is a forced path? All of the urban maps have buildings you can't go into. If you could go in them the maps would take two days to load and would run about as fast Dick Cheney in a marathon. On Odessa the main objectives are pretty much set up that none of fake building facades come into play anyway. They are set back or away from them.
As for the rain, Krasnyi Oktyabr has great sound effects, like when you are in the tin room in the Garage that the Germans often enter into, the rain on the roof sounds excellent!
Baskin looks like it would be bone chillingly cold, raining but still cold enough to have a frozen river? Brrrrr. Actually I would never try crossing river ice when it is raining and all the snow has melted off the grass. If they could, they should have had the rivers with some ice that breaks up or even now ice, but a current that was hard to cross through and made you a easier target. As it is now the rivers are just like roads to run on. But I still LOVE that map.
. I would just use new textures and new stat meshes (holy **** im sick of that yellow carpt 
