From a purely rules point of view, the Soulgaze power states (YS174):
Application of the Sight [+1]. If you have the Sight, above, you may take Soulgaze for free if you so choose. It’s not mandatory.
My interpretation of this is that it's saying that although Soulgaze can be purchased as a standalone power (which would require a template/concept that allows for it), it can also be bought as a (free) upgrade to The Sight. Since Sorcerors can buy The Sight as an option, this would let them buy Soulgaze as an application of The Sight (but only as an application The Sight). Note that there is precedence for this on OW154: Gregor, the "charismatic sorcerer who ran a cult/coven that Charity Carpenter belonged to twenty years ago" has Soulgaze, despite being a 'mere' Sorceror.
It's also unclear that you need to be part of the White Council to be a full Wizard. Clearly the White Council likes to think this is a requirement, but there's precedence for non-White Council Wizards, as well. For example, while Elaine, who was self-taught after DuMorne's death (unlike Dresden who completed his training with McCoy) and never formaly made a member of the White Council, is nonetheless considered a Wizard. And its not clear (yet) whether Kumori was ever associated with the White Council, yet she is considered a Wizard.