As a spin of to the lens pouch project I came up with
this lens coat like protection in neoprene.

Made from the same wet suite as I used for the lens pouches and inspired by lenscoat.com

I used the parts that was to tight to be used as lens
pouches, they become just perfect to fit tight and secure
on my new Sigma 150-500 OS lens.

They will protect the parts of the lens that are most
likely to be scratched on a long and bulky lens like the 150-500 OS.

Cut and fit from the part of the sleeve that fits your lens and the particular area
to be protected.

And like in the lens pouch project, make sure to secure the stitching with some
flexible strong glue!

Done!

This could be developed to a far more complex project if you want.

Soft plastic windows could be stitched into place to cover and protect but not
hide the control switches and scales that are on the lens.
I leave that to you I wanted to keep this project as simple as possible.