I've dabbled in this but one runs the risk of mental illness if they get somewhere with it. It's important to understand that mental illness isn't something you either have or don't have. It's actually something you can develop as a result of things within and outside of your control. For example, your brain chemistry might just go out of whack for some reason by itself without you doing something to bring it on and that could result in manic behaviour, which could result in insomnia, which could result in psychosis. Another thing that's outside of your control is you could survive a plane crash in an ocean and get severe PTSD which could involve things like dissociative identity. Now, what I'm going to say next is controversial. While it is accepted that doing drugs can bring on mental illness, it is generally suppressed or denied that special practices can bring on what would be perceived as mental illness by a western educated psychiatrist. There's a fictional book trilogy called, 'The Illuminatus Trilogy,' and a couple of people have told me they blame it for a brief period they had of an altered state of consciousness, one that would be considered a spell of mental ill health by a mental health professional.
Very few people seem to know and even fewer admit that mere information can bring on strange subjective experiences. A person having an episode of psychosis can sometimes persuade someone close to them of all the same delusions they have. All of this is obvious to people that view things from outside the box and pay close attention to what's actually going on. I have friends that have become religious fanatics and ultimately that transformation was simply just information imparted to them in a particular way. Because religious belief falls under cultural conditioning it is exempt from psychiatric diagnosis and intervention unless the person is a harm to themselves or others.
What I've written above is just a caveat because what I say next will speculate pretty far out. I've read of authors that don't know what their characters are going to say next and they even look forward to finding out when they sit down to write the next part of their current story they're working on. That's the autonomous aspect of the tulpa, which is probably the most difficult aspect to achieve. I've many times interrogated dream characters for information I don't myself already possess to estimate whether they're in any way conscious or can be the source of new information I can use in my life. For the most part, I've not managed to learn anything new from them, however, a couple of times they've managed to word things in a way or in a certain pattern I wouldn't have been able to do myself, and one of them managed to do it in a way that caused me to take meaning from it, as if he did know something I didn't.
On the subject of obtaining new information, I've found that most of what we come to know either comes from learning it from somewhere or discovering it by accident. There's a competitive video game I play, and I've noticed my style is based on things people have done to me and things I've done myself by accident that turned out to be good and I've subsequently remembered so I can use them again and again on purpose. Creativity seems to be rearranging things we already know rather than literally creating something brand new from scratch. What is interesting is that we can certainly learn things brand new to us from other people. If it weren't for that, perhaps we would suspect other people of not being real, like most of us do of dream characters.
There is an audio book I took pains to listen to and largely regretted having done so, called Quantum Jumping by Burt Goldman. In it, he lays down an immense about of twaddle albeit very confidently, but in it there is the idea that you can connect with versions of yourself that have different skills than you have. The idea is that if you can have these versions of yourself communicate an idea to you, you might be able to use it. It's based on the idea that there are literally other yous in other worlds, and of course some of them will have what you want but don't have, and the idea is that somehow if you can get little tips and insights from them you can improve yourself. One of them might be a pianist and able to direct you in that regard. Now, my criticism of that is that you can easily buy DVDs that teach the piano and the teacher in them will definitely be real, not imaginary, and will definitely know how to play the piano and be able to offer you knowledge you can use. I dare say if Quantum Jumping works and is real, it will still be the harder way to learn the piano, not the easier way!
When it comes to a tulpa, one thing that would be impressive would be the skill of allowing the tulpa to take control of your body temporarily. If the tulpa was an expert in martial arts, it could be used to enable you to win various competitions, if it was a competent enough tulpa in that regard. Again though, I think it would be much easier to actually learn martial arts and do it yourself than somehow fashion a tulpa that takes control of your body. That's got to be the longest, most scenic route possible to achieving fighting ability, and that's assuming it's even possible. I suspect it is based on my experiences and knowledge. There are cases of dissociative alters being able to speak languages fluently which are unknown to the host! A martial art certainly wouldn't be a problem if that's the case.
I've read of a woman that suffered from severe hallucinations that developed control over them. She later used that ability to hallucinate images over paper and canvases enabling her to draw and paint them perfectly. Imagine being able to project all the outlines like how it is in a colouring book, and just needing to fill everything in. That's basically what she could do using her hallucination ability.
The question of autonomy is important because without it, it would just be you, and you aren't going to get something new to you from you. You'd want the tulpa to have autonomy so you can learn from it and not know everything it is going to say and do beforehand. This seems like doing it the hard way though. There are scores of books available on amazon written by real autonomous people full of information you definitely don't already know and some of which you can put to use, even if much of it has been handed down or discovered by accident by someone else and then remembered because it's good.
Terrence McKenna apparently had a bit of an obsession with trying to obtain information from DMT elves that wasn't comprised of what he himself already knew and according to his brother he never succeeded.
I reckon it's possible but I'm certain that amazon is superior to tulpae and getting more superior with each year that passes. If what we can create is based on what we know, then we should seek to know as much as we reasonably can, so we can create the best that we can.
David