1. IT still slowhack, and do not make sense since newbie clients never change cl_allowdownload from the default "1", if some player change it ti is because he know how to activate it again
2. SV_ConnectClient still not work if the player is not entered in server, you can't just set a cvar or send an command from players that is not connected to server anyway.
3. About slot, i will say it again: Can be easily done
You have create a problem that is not exists in a normal way