Was what I wrote comprehensible, even if you found it unnecessary? I'm truly not interested in simply applying the Multiclass move, though I appreciate that others prefer that.
I agree that what you wrote is comprehensible and I also agree it is totally unnecessary (see below).
In addition, why the restriction on Alignment? You can pretty much change your Alignment and or/Alignment Move at any time per the core rules as long is there is justification in the fiction.
Maybe easier just to say "if you justify it to me in the game fiction, you can always pick a multiclass move on levelup".
There's no question that what you suggest would be easier, but presently I'm interested in making it feasible for one player to eventually take on the entire role of two classes, if they wish to. The point of this system is to figure out a way of doing this which isn't too immediately overpowering, nor completely unappealing.
I'd ultimately like the players to be able to expand their move options beyond what is offered by a single class progression, regardless of whether they can take Multiclass moves. I also see the gaining of a new class as a great roleplay opportunity.
I'll echo the sentiments of others by saying that allowing the Multiclass move at any level with in game justification achieves your stated intent in an easier fashion and with much more flexibility than you are allowing.
On top of just allowing the Multiclass move at any level, add a single rules tweak:
Multiclass MasteryWhen you have obtained all the Starting Moves of another class, you have mastered that class; at this time, between your starting and mastered classes you may choose the best from each of hit points, damage, and load. You may also choose a Racial Move/Background that is appropriate to either class.