Thinking of tulpamancy as compartmentalizing positive emotions is an interesting way to look at it. When my host accidentally created us, it was an excuse to "talk to herself" without getting immediately sucked into self-hatred. On the other hand, I'm not a happy-go-lucky butterfly either. I may have been more like that when I was younger, but now that I'm more developed I'm more well rounded than I was.
I would be cautious when comparing DID to tulpamancy, while both have some overlap there's a lot of fundamental differences between the two.
Creating a new tulpa just to deal with intrusive thoughts is unnecessary, but working together as a team can help.
You may be interested in reading this thread: https://community.tulpa.info/topic/15163-mask-tulpas-a-rare-tulpa-origin/
I don't completely agree with that model of explaining how tulpas or alters work. I'm more than just some version of my host who's online all the time, likes English, and has a thing for hippos. I'm also not one of my host's emotional states.
You need trauma or a dissociative disorder to have extreme medical dissociation. Tulpamancy isn't a safety feature that can prevent DID.
Kids making imaginary friends is now called normal in the United States, and for some tulpamancers their tulpas were their imaginary friends all along. This has nothing to do with experiencing something traumatic.
Consider this: My host made tulpas out of desperation because she had no one to talk to about her pain, she was lonely, and she didn't want to talk to "herself" because she hated herself. But my host was not traumatized. We're autistic and my host was struggling in school, and she internalized her parent's frustration to the point where she used wonderlanding as a form of escapism. But she wasn't physically abused, her parents loved her, we live in a safe place, etc. My host used tulpamancy as a coping method, but there was no risk of her dissociating because there was nothing traumatic for her to experience.
Trauma in of itself does not always cause a dissociative disorder, but if you have a dissociative disorder you almost always have a trauma history, especially if you have DID / OSDD.
When my host joined the forums, she wasn't interested in tulpamancy for switching, her mindset was never "I want an alter". Her goal was to make sure I was happy and healthy since at the time, we didn't feel safe in our own head. Controlling the body was something I wanted to experience once I decided I wanted to explore that, and as I developed I wanted to learn switching.
I do this only if it's something I like more. I like to clean more than my host does. I like English class more than my host does. We both share a body and I want to do my own things, so why not let me do it instead?