Of course his mother has the authority to declare a match equal no matter the woman's background.
I'd hoped he and Theodora of Greece would hit it off as that would have been they ideal match but she is engaged to someone else.
After Georgy this get a bit difficult. You would first go to the line of his grandfather's older sister Maria. She married into the Leiningen family and there have been discussions about wether that house would be equal or not. Im not sure if Cyril made any decisions about the status of his son-in-law as there were still male dynasts around who all had rights before Maria and Kira.
In case the Leiningen dynasty would not be considered equal than the line of Kira comes into play and Georg Friedrich heir to the Prussian and German line could be seen as the heir for the Russian line as well. All these lines are protestants and not orthodox. At present that is not an issue but the moment Georgy becomes the head of the dynasty his heir or heiress has to be of the Orthodox faith and if that heir is married the same applies to his wife. Further down the line the faith of heirs and their spouses is not stipulated.
So if you follow that route we might see Karl Wladimir and Dimitri of Serbia come into play. Their mother was princess Kira of Leiningen a daughter of Maria Kirilovna.
Karl Emich of Leiningen is a grandson of Maria Kirilovna and has converted to the Russian Orthodox faith. He has been married twice before his current wife. As the oldest son he did not become the heir in Leiningen due to his marriage to Gabriella Thyssen (after their divorce she married the Aga Khan and divorced him as well). He is now married to a German countess but as he was barred from the Leiningen succession his claim to Russian successions are at the least dubious.
Hopefully Georgy will marry and provide heirs for the Russian dynasty. He might be like the Duke of Braganca in Portugal someone who needs some time to settle down and start a family.