As others have said there are bigger issues than this. Becoming fluent in two clefs is unfortunate, but doesn't take too much time. Adding most lines I could see becoming more confusing and it takes up more vertical real estate. The overall score will expand vertically.
My biggest problem with music notation is it being centered around the key of c major. When ever critiques of current music notation come up I like to bring up the janko keyboard. It has an isometric layout which means that any interval will have the same shape no matter the starting pitch. With this layout if you learn a major scale in one key you've learned it for every key. Transposing from one key to another is just shift your hands. I haven't seen an alternative music notation system which has advantages like this while still being compact and readable.
But what if we simply used 2 F clefs? We'd only need two ledger lines between them for C and E. Given how many ledger lines we put up with above the top staff, I think it would be pretty easy to work with. After 2 decades, I _still_ read treble clef better than bass clef.
This depends on the instrument. For many instruments reading ledger lines below the staff is more common. For instance french horn players are used to reading well below the treble clef staff and tuba players well below the bass clef staff. Standardizing on one clef isn't sufficient to fix the issues in my opinion.
My biggest problem with music notation is it being centered around the key of c major. When ever critiques of current music notation come up I like to bring up the janko keyboard. It has an isometric layout which means that any interval will have the same shape no matter the starting pitch. With this layout if you learn a major scale in one key you've learned it for every key. Transposing from one key to another is just shift your hands. I haven't seen an alternative music notation system which has advantages like this while still being compact and readable.
See here for some experiments in attempts to improve the situation: http://musicnotation.org/