Talk about; damned if you do, damned if you don't.
Sane here, my wife would never go for it. Iwould love to piss all over het while she is fully clothed.
Yes, be careful about this. I don't know why my wife used to say this, but she was always saying something about me peeing on her or in her mouth - mostly while we were still just hanging out together. then saying she was joking (I had no particular desire to do it, I should add). Anyway one day after we'd been married for years she said it again, so I let a squirt go in her mouth. Jesus, was she indignant! I said "You're the one who's kept on and on about this!" Well, she has never ever mentioned it again.
Urinating on your wife's leg/vag in the shower would be an issue? For one, urine is sterile, and feels slightly warmer than the water from the shower. Why not offer to wash her off afterwards followed by licking/kissing her legs and giving her some oral in the shower? I had an ex pee on my leg in the shower, not b/c of any kink, I just wanted to see if she would, haha. It wasn't anything special, but to each their own. There's far more offensive/repulsive/deviant things you could be into or suggest.
I was upset one day while married to someone that just turned my world upside down. She was in the tub soaking in her bubble bath. I walked in, seen the bitch, pulled it out and pissed in her hair and everywhere. Her hands and arms were in motion trying to deflect the stream, but, I was able to piss all over her anyway. Felt good too!