You will need to play with mods to be able to save characters on the server. This means that all the players will need to run mods too. Keep in mind that a lot of players will run away as soon as you mention mods. The mod is called servercharacters and is available at thunderstore.

Another solution is to require a prefix to the name (i use this option). For example, you make a rule that all players have to add prefix Mr. in front of their names. This way you are sure that all the players will make a new character and start with zero skill points, but they will still be able to log in to their own world and spawn whatever they want and bring it back to your server.