Allow us to use tar to make wooden structures water-proof.

I'd really like to be able to create wooden structures like bridges and shit that don't decay without the need to slap a roof over it, as this kills the look I'm trying to go for. A great solution would be to let us waterproof those structures with tar. I'm not suggesting new darkwood duplicates of all the wooden structures be added to spam the build menu. This could be done by creating a single new tool: a tar brush (made with lox fur and fine wood or something). Let us use the tar brush to "paint" wooden structures we have already built so that they don't decay in bad weather/submersion. Since both tar and lox fur are fairly late game, this wouldn't affect the game design's push to force you to build a shelter early on. I know you can remove the decay completely with mods, but I prefer to play vanilla and would like to see this in vanilla. What do you guys think?

Edit: another solution to avoid build menu spam would be to make darkwood duplicates of all the wooden structures, and also add sub-tabs to the build menu, with a separate tab for darkwood structures. This would be way easier for the devs to implement than the tar brush idea.