- "Open Multiclassing" was an experiment in 3e that was interesting and exciting, but ultimately cannot be made to work. You simply cannot give out an ability without knowing what level you will be when you get it and expect that ability to function in a level appropriate fashion.
- Multiclassing at all is basically bad for the game. At its best it is a way to make playable classes that are procedurally generated and therefore take longer in chargen and probably aren't playtested as well as other classes.
- When there are explicit, functional classes that cover a character concept, they are massively and understandably more popular than multiclass setups that cover the same concept.
- Nonetheless, if you tell people that there isn't going to be "multiclassing", people will lose their shit. Even if they acknowledge all the previous points.
- Make actual classes. Announce that some of them are "multiclass" combinations. The Ranger is now a "Multiclass Fighter/Druid", the Paladin is now a "Multiclass Fighter/Cleric", and so on. The main class names are more popular than the multiclass combos, so you'd probably write "Paladin (Fighter/Cleric)". You would probably do something involving the "multiclass" characters being able to pick their skill lists off of the nominally parent classes or something to make it less obvious you were trolling people.
- Sub Classes. Announce that at some level or another you get a power upgrade that is chosen off a list that happens to be a list of themed upgrades that are themed off the available classes. And then you'd get an upgrade that was themed "Wizard" or "Assassin", and you'd announce that because you could get an Assassin Theme for your Samurai that you had "multiclassing" covered.
- Short available Multiclass list. In any edition of AD&D or OD&D only a small list of classes were actually multiclassable. You could be a Fighter/Thief, but you couldn't be a Cleric/Illusionist or Paladin/Thief. So in this model, you allow a small number of classes to be multiclassed, and then you playtest those combos exactly like they were a normal class. And you let people partially procedurally generate these classes so that players get the "joy" of having to make their own classes.
-Username17