The answer is no.
You cannot give a Sorceror attached to a Thousand Sons unit Terminator armor because he is not an independent character.
You may ask, "Why then, can a retinue of a Sorceror Lord be made up of Terminator armored Sorcerors? They aren't independent either." The answer to that is: You give the Lord terminator armor, upgrade his retinue to a Thousand Sons Terminators squad, and then upgrade the Terminators to Sorcerors.
The Space Wolves (and the Iron Hands too, I believe) have special rules (Wolf Guard and Iron Guard, IIRC) that allow them to give non-independent characters Terminator armor.