[2021] Russian Time tunnel

Not sure i get your point here. We've been filling in blanks in tech trees since day 1, using either designs for ships that were planned but never built, or even drafting designs from scratch based on the prevalent paradigms present in any nation during the period in question (based on available sources).

It's obvious that the longer we run, the more of such designs we will have in the game, because the available historical ships will be in classes that are already present.