Transitions between Main Professions are generally related to factions.
A Tier 1 faction can switch to a Tier 1 Profession, and a Tier 2 technology can transition to a Tier 2 Profession.
For example, if you're a security guard at a large corporation, then at level 10, you can transition to become a 'Prosthetic Body Security', an officially employed guard with a contract. At level 20, you become 'Mechanical Special Service', with 50% of your body prostheticized, and at level 30, you become a 'Pure Mechanical Guardian', achieving 100% prostheticization and entering Tier 2.
The same applies in Gao Gong's own faction: a level 10 Ordinary Hunter, level 20 Wild Hunt, level 30 Blood Hunter.
As a Tier 2 faction, even breaking through level 30 doesn't mean there's no equipment for you. For instance, prosthetics of higher class, biological chips of higher class, allowing you to upgrade your profession to a higher level.
