I'm tired so I'm gonna number the issues and not split the quote.
1. I'm home on vacation (the Sukkot holiday) for the next ten days or so, I'll write as much as I can about the tech tree either later tonight or tomorrow. I'll be online pretty much every warking moment over the next few days, so we can keep in rapid contact... Just a bit busy and tired at the moment.
2. But I guess I don't mind if the Byz change is made in a civpack - as long as the civpack is for RoX and not RoC, because I will probably stop playing RoC once RoX is out. (RoX rocks.

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3. I mean, give the romans a different Warrior (same animations, same stats, same cost, just different upgrade path) that upgrades to Legion. That way once Legions come in the Romans will upgrade all their spears and warriors to Legion, and in the middle ages they will have to build a brand-new offensive armies as the Legions will merge into the Spear line.
4. But there is a No Upkeep flag. What I'm proposing is high shield cost, but no upkeep. As I said, mercenaries supply themselves (and upkeep is not payment, it's support and supply), you just pay them for their work. But as I said they may have no merit at all for inclusion, just an idea.
5. Ask someone else, I'm not very knowledgeable in this field.