That sounds like a fun project! Keep us posted. Bear in mind, it will be expensive and require a lot of work. It takes a lot of plants to take up the nutrients of swimmers, fish, and debris that will enter the pond.
A thought would be to provide yourself a clean-out drain if possible. If it is only a pipe plumbed to the deepest section and brought to an edge that you can connect a trash pump to in order to pull out a bit of accumulated gunk. If you get the water circulating via pumps, you can direct this gunk to the middle to be removed every so often.