But Maria’s mother’s branch doesn’t belong to the ruling branch of the Bagration family and some say her mother was a divorced woman.I'm assuming the right to use the dynastic surname Romanoff* is decided by whoever is the head of the family of pretenders. In the case of the Romanovs, the amount of family quarrels is their worst enemy since there's no united front. Reminds me a bit on the 19th century French restoration quarrels between the House of Bourbon vs House Orleans.
* Footnote - the last Romanov by blood was Empress Elizabeth and her then nephew Peter III. After Catherine the Great the surname was used by her surviving descendant from Sergei Saltykov, she had two miscarriages and then Czar Paul I with Saltikov. Catherine also had three other children after Paul.
In regards on whom I give the upper hand in terms of lineage, hands down to Grand Duchess Maria. Her mother was a Bagration royal princess whose family had to scale down to serene highness when they were absorbed by the Russian Empire. I recall reading ages ago some article that the reason why princes in Russia, from independent pre-Rurik and Romanov estates, did not meet equal status with the German princes of the Holy Roman Empire was caused by the Almanac de Gotha system to catalog the titled royal houses and nobility.
Like if a Russian prince that ruled over an independent pre-Romanov territory was not equal to a German/Holy Roman Empire prince, duke or grand duke that also had an independent territory in Central Europe. Don't know if the reasoning was the Holy Roman ruler was elected by the equivalent today of state governors but titled kings, grand dukes, dukes, princes et al. While in Russia one family, the Rurik and later the Romanovs, made it hereditary but absorbed all these independent states.
This reminds me Spain was formed by the union of many kingdoms and people who descended from these small kingdoms today became Dukes and Grandes like the Dukes of Medinaceli instead of being addressed as Prince of Medinaceli, etc. as they did in Russia, the Holy Roman and later German empires.
In terms of Maria, from her mother's side if she was installed as Czarina today, she and her son and grandson's dynasty would be older than the Danish royals since the Bagration dynasty was around as far as the Roman and Byzantine empires while the Danish line started, I recall, since the year 900s (?)
Article about the on-going family drama, first published in 1998: The Romanoffs and the Bagrations