There was a CLEO script you could download to your game which does this for SA:MP already. I think it was called reconnect.cs or something.
It allowed you to /recconect or /connect or /name (to change the name you are connecting with & reconnect) and came in pretty handy tbh.

I used to use it frequently, I don't know if there is a benefit having it hard coded into the client in all honesty. It's something that more hassle than it's worth.

I haven't touched it in a few years since getting a fast computer though.