In a recent post on the HGA, Conjureman Ali addresses the idea of having multiple spirit Assistant/Guides, one for the Celestial realms (the traditional role of the HGA in modern interpretations of the Abramelin Rite), and one for the Chthonic. On Moloch's EvocationalMagics yahoo group, Aghor Pir, Aaron Leitch, and Conjureman Ali have discussed the topic a bit.
To summarize, we all agree the Abramelin HGA has a primarily Celestial role. Aghor discussed how his Genius from the natal chart (as in "Genius and Evil Daimon") seemed to be a Chthonic entity, and that the Supernatural Assistant he received using my course materials was of a mixed Celestial and Terrestrial nature. Aaron talked about how the combined nature of the Supernatural Assistant was split in the Abramelin rite, with the celestial roles going to the HGA and the terrestrial roles going to the demons. There wasn't any argument, which is nice. Lots of mutual respect.
My take on it is that all the spirits, the Supernatural Assistant, the HGA, the Angel of the Nativity, the Genius, Scirlin of the True Grimoire, they're all reflections of a single Idea in the mind of God. I think the "Helpful Spirit" is the Idea that manifests in different ways for different people in different cultures, and that there are many approaches to find the kind of spirit that will function best for your needs. You may find one spirit is of mixed nature and is more than sufficient, or you might find that your HGA name harmonizes with the celestial spheres, but a blood pact with Scirlin is more effective for working with chthonic entities.
A lot depends on your worldview, your cosmological view, your experiences and training, and the things you're here to do with your life. Your culture factors in, the religion you were raised in, the morals and values you absorbed and formed on your own.
I've been reading Geosophia and True Grimoire by Jake Stratton-Kent lately, glowing reviews to follow, and there's something he does in those works that is simply beautiful. He removes the false divide between the Chthonic and the Celestial. At least, he did for me. I don't know if he did it for everyone, but I suspect that was his chief aim in writing the books. He blew the lid off the Great Secret in ways that no one has done for me in a long time. Flipped my lid.
There is no heaven, there is no hell, no Celestial/Terrestrial divide. Those are descriptors of various points on the spectrum of experienced cosmos, but imperfect ones at best... and lies, damned lies at worst. There are demons who want to ascend and unite with the godhead, and there are angels that delight in war and murder. The heavens of Theurgists and the hells of the Goets were the same places in the old days. The forms evolved, but the essence, the stuff that really matters to magicians remained the same. Magic puts us back in conscious interaction with our fellow spirits who inhabit every plane, all at once, in various forms, each a manifestation of an Idea in the Mind of God just like us.
But then we get to the complicated parts. There are parts of the spectrum that are best described as celestial, and parts that are best described as chthonic. Goetic magic is not celestial magic, and the HGA is not the Supernatural Assistant, is not the Genius, is not Michael, is not the Hagios Pneumatos, is not Scirlin. Different systems give us different results, and I think it is wrong to say the Genius of your Natal Chart is the SAME SPIRIT as the HGA. They aren't. They feel different, they are reached differently. But the practical application of their role in your life sure seems to be the same for all the magicians I talk to. They teach, empower, and connect you to other spirits as needed. They protect and attack for you, or at least coordinate attacks for you. They can be faithful lieutenants or generals, depending on the role you're best suited to taking in your situations.
I think the most important thing to remember in these discussions is that they are discussions. Conversations, words that point to ideas, but remain approximations only. They can guide our actions, but I think the most important thing we do with the results of our conversations on the subject is the part where we actually take action. Whatever "Helpful Spirit" model or models work best for you is fine with me, I'm much more interested in talking about what you do with the relationship with the spirit you have than anything else.