I'll keep editing this post and putting ideas down as I think of them

.Obviously it needs a name amongst other things.
.I reckon that we should be the Saxons. I know it's a diff. time period, but Vikings would be cool. Romano-Brits sound fun, but certainly not the WRE, Huns and not the ERE either. Suggestions/comments...?
.We would need to find a good time frame. If it were Vikings it would be much later, but if we were the Saxons or any other barb. faction, we need someone with good hist. knowledge (even though I myself will have a look; I just want something to compare with / a second opinion) to propose a good starting date.
.It will need to be centred around a Barbarian council, but it's NOT going to be called 'You are the Council' - that's boring, unoriginal, and people couldnt distinguish it from the current YATC. SO it'll need some developing here.