They were working with scraps for Leia, and much more than we have. I am open to mock-ups but I don’t imagine most of these being improvements. I’ve been wrong before and it doesn’t hurt to try and see.
About the end scene, black would make sense for a funeral but it still feels like it signals the wrong thing. I agree grey might be nice, but it’s still the same outfit and I feel it’d be obvious it was merely recolored. I’d really like to see a return to what she wore at the end of TFA and most of TLJ, really. Or just something new. I imagine they had her revert to her scavenging looks in order to fit with footage of hugging Carrie from TFA. I really think that’s most of the reason why.