Hi! My suggestion for a change in the game does not concern gameplay or anything. It is a little annoying that there is no "wait for an open slot" function in the join server menu. There are usually a lot of servers online but most of them are full and generally don't seem to kick idle players. Therefore, it can be very tiresome to find an open slot on some server by clicking the refresh button for like a 1000 times.
My suggestion: insert a feature like "connect to server once a slot is open"-thing You can check in the steam menu when, for example, waiting to play on Your favorite tf2-server.

Maybe this is not on Your priority list but I tihnk that a lot of my fellow gamers would agree that such a feature would be awesome!

Unfortunately I think this one is up to Valve, not Unknown Worlds, as the server browser is part of Half-Life's engine and isn't publicly modifiable.

When looking at the server list right click on a server and select "View server info". Click "Join Game" and when that fails an "Auto Join" button should be available which automatically attempts to join the server every second or so.

You can definitely get this menu to appear if a Friend is already on the server by using the "View server info" button through the friends list. I can't quite remember the layout of NS1 server list but I seem to remember it uses the same Steam one so it should be possible to do this?