@mmirG I was less thinking about the GUI (I'm actually a fan of most features of the current layout) and more just about providing a simple means of connecting translated release groups. However it's displayed -- as a text link in the "Relationships" list, or as something making use of modern web features -- I'd say we'd benefit from an official means of indicating that translation, and unless we go with series, that's probably going to need a small change to the database structure.
My argument against series is basically that, while translations fit the first half of the definition in the documentation ("A sequence of separate release groups [...] with a common theme") they don't at all match the second ("the individual entities will often have been given a number indicating the position"), and it would be essentially repurposing "series" as "group of release groups". I've had a bit too much experience with the mathmatical definitions to think of a sequence as equivalent to a set, but if that's something the community here sees as overly-detailed semantics, then a series would probably work.
By the way, the Blue Note example on that page only has a single member. A casulty of merging?