After talks with the factory, we decided to give the polycarb plate option a go! As said in the main post, it won't be prototyped like the Black Nickel kit, and will be an extra with a MOQ of 5.
From my test of using acrylic plate, it does have some areas with pretty significant bending, but still usable if you're not heavy handed. More importantly, it looks quite pretty, so I want to give it a try.
Some pics of an acrylic plate with the protective film on:
It costs me what it costs you, $60USD.