Well if the unit has a generic name mentioning a tribe (as some of existing German units or proposed mod units) i suppose you'd have to figure out how to write it in the specific name.

Do you really need to know that for a unit?  

I suppose  you just treat them like personal names without inferring meaning then. That can actually work (they probably had some meaning in real life, but we can't necessarily know it) I was considering suggesting some names for mod units and was in doubt about that. Specially what to call the Cherusci or Chatti.  A lot of people associated the Cherusci with deer (herutaz) i was questioning whatever it could be derived from ''heruz'' (sword; heruskoz would be something like the ''sharp'',''sword like'', ''sword-esque''). Or whatever Chatti could be related to hatjaną (hunt, attack, pursue), hataz (hate), or haftaz (captive, bound. As in Germania it is mentioned some of them wear iron rings until they kill an enemy; and that this is seem as shameful by other tribes).

Yes, there are sources recording they were deployed along cavalry, but since they are never clearly described as fighting as cavalry (as far as I remember), probably they could have sometimes fought like hamippoi (those running alongside horses). This and their "unclear" role (or maybe "varying", across different periods) is what led me to propose in Thoughts on the Spartans for them to be "faster and with larger FOV" to "balance a weak cavalry", and given that Spartan hoplites should be particularly slow, as mentioned a few comments back

In older 0ad Versions Civilisations had more differentiations. Then some releases ago there was done a lot of work to make them more balanced. I think there were reasons for that. Altough I am happy that in the two latest realeases there were new differentiations to make the game more interesting. At the moment I rate Athenians highest especially in no Champ-Cav-Games.  Although in early game phase I think gauls is strongest. If you manage to boom in late game I think Mauaries are underrated.  But if you have to fight an army of 50 elephants mele and ranged..... I think there should be limitations for that heavy units. When you face 20 rams or catapults its also gg, at least if there is a minimum companion army on their side.  Maybe you are able to smash the first fiew of them but then everything gets wiped out. Persians and Han can are also very strong if you manage to built a large cavallery.