Biohazard

Just so you know those 1" spaced wires laced thru the burlap were spring steel.
The reason they are used over the coil springs is to spread the load across the
seat. They are meant to spring back to straight once a person leaves the seat.
The only reason the factory used burlap was cost and a carry over from a time
before the age of synthetics. If you wanted to you could use a polyester marine canvas
such as Top Gun that eliminates all the negative properties of an organic.
You can also get paper coated wire new. It is spring steel made for seat rebuilding.
If you wanted to seal the paper just soak them in some thined paint for awhile pull them out and let dry.
You can replace the cotton with foam also and you would have a choice on the density.
When building seating from scratch it is desirable from a comfort perspective to stage the
foam. First layer very dense so you can't feel the springs. Second layer medium density.
For a car seat you would not need any soft foam like a couch would have.
The vinyl seat covers are much to rugged for the top layer of comfort foam to be of use.
Looks like you are figuring it out. I like the red covers.