Because of the resemblance to the (newer) Medusa bomber, I would see "GTB Euryale" as the name much more fitting than appending a simple "Mk II". And even in Grecian mythology, having two vessels named as Euryale is appropriately fitting, since the other was the daughter of King Minos and mother of Orion.
However, in going with the mythological reference in which Medusa is named, there is also the name of one of Medusa's offspring when her head was severed, which was Chrysaor, which might also be fitting. Granted, it (Chrysaor) was told to be a Golden Sworded Giant (which this isn't, necessarily) but it shows the lineage of inheritance to the Medusa more so than it speaks to me of being a related to Medusa, especially if it's leveraged in a Strike Bomber manner which it's shape seems to suggest is its potential.