back in the long-long ago when i was online dating, the biggest boon it provided was that it gave you a space where you knew that it was okay flirt and that your intentions would not be misunderstood. you never had to guess if it would be a creepy time/place to flirt. you never had to worry about your intentions being misunderstood as "just being friendly". if somebody was on this app/website, they were looking to flirt and if you approached them everybody was clear that you were flirting.

doing something similar with friendship could be great.