I think OGS should copy this feature from Lichess. As a very casual chess player this is how I play most of my games. I click ‘Play with a Friend’, chose a time setting and then send someone the link. The sender and recipient don’t even need to create accounts, if they aren’t logged in then they automatically play as a guests (and the games are of course unrated). Often I will just post the link to a group chat and play the first person to click on it.
I would personally use this feature a lot if OGS implemented it. It would remove another barrier to casual games and would also speed up the process of challenging specific users. You wouldn’t have to go through the steps of finding out their username, searching for it, and sending a challenge. It’s a lot less clicks, which makes all the difference.
OGS already has the major advantage of being able to quickly share links of ongoing or finished games/reviews, so this feels like the logical next step.