Ok with that I can agree...
But imo top criteria to include faction are these:

- Somewhat independent and relevant at the start date.
- Enough evidence to back it up properly.
- Expansionistic desire.

Now I don't know what the team uses, but including the Pannonias is comparable to the Eburones the way I see it, I think the suitable ones for the area are Skordiskoi or Illyrians...
Maybe we'll get few hints or a preview soon, who knows :P