Perhaps have the water be a layer of ice? That would be an interesting change to the map. And it would only really affect the water under the bridge, game-play wise.
It isn't too late to start. Even if there are multiple versions called "ctf_snowfort", it certainly isn't too late to release "ctf_snowfort_v7" or whatever (especially when the map continues receiving updates )You're right, I neglected to do that when I released the map, I'll be sure not to do that for future maps.