I still don’t know if I’ve understood correctly what you are trying to explain.
But, from what I have understood, I don’t see things on the same wave length.
In my opinion, split personalities happen in case of trauma that causes a disorder in the primitive part of the brain. The part that regulates instincts and emotions. It is then the instinct (survival instinct) that forbid the cortex to use the usual personality, and forces to behave on a very different way that doesn’t correspond with the initial natural personality and is a kind of mask .
When the trauma is treated with techniques like EMDR for instance, the split personalities disappear.
It works much more like healing a wound. The split personalities are more like something « broken ». And it can be « repaired » with a psychological technique.
On the other hand, what Joe Dispenza is proposing is to initiate new brain connections by changing our habits and our beliefs. This can transform our brain. In fact, I don’t know if Joe Dispenza is proposing to seek a change into a "new mind" or a « new personality ».
If he does, I probably then don’t agree with him.
For, in my opinion, we can learn new abilities that are probably very different from the ones we had before, but this doesn’t mean that we change our personality. We are staying the same person.
And I consider that keeping our personality is important, because our best potential is in our own personality. What we need is to heal all our psychological wounds and to learn to use that personality at her best. For, the best of oneself lies potentially in one’s wounds. So that, healing our wounds is our force and makes possible to develop the best part of our personality.
And if we try to change in a "new mind" or in a « new personality », we completely loose that possibility, we are then throwing away our best potential.
But this is only my opinion, in fact.
However, what I begin to glimpse (have an insight of) is the fact that our brain and personality evolution, can lead us to transform ourselves so fundamentally, that it could be as important as a caterpillar transforming into a butterfly. But still, it wouldn’t be a change to a new personality or a change to a new mind. What we would become should be based on what we were in the past.