I was going to say "But wavelength/polarization multiplexing is the norm", but you have "fiber network design" in your about so I'm wondering what I'm missing - I guess you mean dynamic muxing, essentially routing? SerDes is of course annoying.
Yes, being able to do anything dynamically in the optical domain would improve things.
My main point is that to be able to do even the small stuff in the optical domain would be a big win. You don’t need to be able to achieve L2/L3 switching/routing to move the needle.
Basic things like optical muxing/demuxing and serialization/deserialization would be fantastic.