My vote is for simple, fast, cheap, light, and easy (anyone wishing to steer this line of thought toward the subject of 'women' can start a different thread).
I like a piece of sheet steel just big enough to do the job and not much bigger. Scrap stuff is fine. I like one little hole to slide the deflector over the launch rod. End of design.
I do not like a big block of ceramic or other material that costs me $5 and that I have to carry out into the field with the launcher (sorry, even if they work nicely, I'm too lazy).
I like something that if it gets lost in the garage, or the kids ruin it while digging holes in the back yard with it, or if it burns through, it's no big loss.
An overlooked source of thick (1/8 inch or so) plate stock is your local welding shop scrap pile. I got several discs (approx eight inch diam) roughly cut out for me for $5 a couple years ago. Catch the shop guys on a slow day, and they'll probably be quite willing to help you out.