If you try to pursue a platonic friendship with someone you are crushing on, that has the potential to turn quite ugly, speaking from experience. Obvs you know the situation better than me, but one might say that carrying on like that is even dishonest/unfair to both parties. It will be way harder to salvage a friendship if this comes out later on, when you both know you've been continuing under false pretenses.

As for appropriateness, there's nothing weird or creepy about asking someone out! You can even lampshade the awkwardness it if needs be. You're making out that boundaries were set when you spoke with her. Is that true? Because asking her out is how you give her a chance to set those boundaries.

I can’t speak for you, but trying to be friends with people who don’t know I have a crush on them, with the goal of never telling them and hopefully moving on, has made me want to put a bullet in my brain. Especially when we become closer and I realize I still liked her. The only way I found any inner peace was by sabotaging it, i.e. telling her my feelings, and ending the relationship. If I could do it again, I’d tell her from the get go. Being rejected doesn’t mean a friendship cannot form, but being rejected when a relationship already exists is much more soul crushing and unlikely to lead to any alternative relationships.

Rip the band aid, and maybe one day you’ll both look back and laugh your asses of as best friends who truly care and love each other, but just not romantically. Or who knows, maybe it all works out.