Problem with Roman Highways as Epeiros

[Hax]

Would allowing other nations to build highways be save-game compatible?

Yes, it's savegame compatible.

I would think making it possible for all 'civilised' civilisations would be a good idea, maybe tie it to the march of time given that you want to delay the introduction of roman technology

I don't know how you tie things like that to the MoT event. Oh well.