Gorgeous but damaged vintage 1960s blue dress with overcoat half sleeves

Okay so this dress ended up getting damaged while I was trying to gently soak in some set in stains out. I used the wrong detergent and while it did lessen the stain (shown in some pictures, brown) it also bleached parts of the acetate lining that apparently is not colorfast. I have to admit I am not a vintage expert; I am mostly selling items that belonged to late family members. I am so bummed out about the damage this piece took, but it's still got good bones and some amazing details. I'm putting this for sale with some wiggle room for offering because I do think this could be saved or altered into something cuter and more modern and I would hate for it to go into a landfill. The lining is acetate and I think the outside is also polyester or a poly blend of some sort based on how it feels. It needs an iron and it has a small spot of detergent stuck to it but I'm too scared to go back over the fabric in case I ruin it more!! The long sheath dress goes down to my ankles so it's a full maxi and would likely fit about a 27-28 inch person, maybe a little bit smaller than that. It was hand made and there was no size on it. I have it listed for 20 but I am looking for best offer as well. The collar has stunning and beads that are in perfect condition.