> Asking permission before touching people, and not arguing when they say no goes a long way.
Honestly, that's just not realistic. Subtle touching is a key part of rapport and bonding (even in a platonic setting between men). It would be extremely bizarre if after a woman laughs at a joke I stopped and said "is it okay if I gently touch you on the elbow for a second as you laugh?"
I'm a huge fan of consent (ex. I almost always ask before kissing anyone) but that doesn't mean we need to extend it to absolutely everything. Humans are set up to be able to send touch-based signals which can escalate while allowing plenty of exit points.
We don't need hard rules like asking before ever touching another person (what if I accidentally brush against someone walking through a bar?). We need better training on reading social cues and a culture which calls people out when those cues are ignored.
A key part of healthy, mature flirting is leaving plenty of exit points and respecting them. Ex. it's normally fine to brush your leg against someone's leg. If they're not interested, they'll quickly pull away and it shouldn't cause too much discomfort. If they are, they'll maintain the contact.
TL;DR bodies can communicate. The problem isn't with these communications being non-verbal, but with people willfully ignoring those communications.