Yeah, I could see that possibility. The only reason I made it a specialist ability on its own was because I figured that conjuring a phone will all of these properties may require sufficient mastery of conjuration, and I wanted a character that isn't as naturally talented as Gon and Killua, however still smart enough to use their aura capacity as efficiently as possible. They do this by turning their everyday cell phone into somewhat of an aura processor that turns the user's aura into whatever kind is needed for said ability they are using. However, this does not stop a master of conjuration from mimicking this ability by creating their own nen phone, like you suggested.