Suspended floors and better bridges

While doing a sewers map, I wanted to put some kind of iron grates from the floor section in a way that allowed the water to pass underneath it. Atm, iron grates create a brick structure underneath when placed, and that blocks water and ends up being suspended over nothing.
Also, available bridges are a bit too big and not really customizable. If we could have just a bunch of "bridge tiles" to use as flooring material, it would make it easier to create suspended structures without having to relay on whatever pre-made structure is available in the bridge section.