Dear Darth, I do not think that it would be fruitful to try to stick with being too "historical" with these names. I believe that the fact that you would have several different names (some of them with geographical connotations) for a single number of legion (like I Adiutrix pia fidelis, I Italica, I Macriana, I Flavia Minervia, I Parthica, etc.) will be just confusing. I am becomming more and more convinced that we have basically two options here: either (as it is now in the Atraphoenix´s mod) to have numbers without any particular geographical connotations OR to have geogrphical names based on the city of origin. Those two approaches are basically mutually exclusive.

Now, there might be a way how to satisfy both. You coud assign numbers through ancillaries, going from I to XXXV in sequence. You could even spice it with names that were historically used but bear no particular geographical or temporal connotation (like Adiutrix pia fidelis, Firma, Victrix, Ferrata, Apollinaris, Rapax, and such). This should be open since the beginning of the game, i.e. for Camillan and Polybian era as well.

The proper geographical element might be introduced by allowing recruitment of first legions in certain regions and encode proper geographical name for them in descr_regions (like Hispana, Gallica, Macedonica, Parthica, etc.). The fact, that due to the hard-coded part of the legionary_name attribute such first cohorts will also get a number (sequentially from I to ...) could, IMHO, be safely disregarded.

The more nerdish player could easily make sure that the number on his Legionary banner (ancillary) will correspond with the RTW-engine-assigned number of his first cohort.

Please note, that the "geographical element" is a part which I think as optional add-on, not least because it decreases compatibility with other mods and to mee it seems superfluous too, because roman history fans could easily imagine the proper name of a legion if they have the number and its current in-game location.

I am firmly convinced that the sub-mod shall be opened to players who did not want to be tied too strictly by history and as each and every game is developing somewhat differently, the mod shall allow for it with much inherent flexibility.