The easiest would be to use BPCore and use it's Skinning functionality to override the MSD maps with your new ones.
It's the "NormalMaps" part.
You would basically create a new bridge plugin, with the new name, if I remember correctly, it was safe to re-use bridge files (in scripts/Bridges), so you only need to copy the plugin from the original bridge you want to base your new bridge on, and then add the NormalMaps part to it.
*Moved to Bridge Modding*