I think Firaxis would include a fairer Celtic representation at some point, I just was expeting that the Gauls would happen in a second round of passes, not this one. That said, I find the Gauls much more interesting to represent the Celts than Scotland. I just find Scotland's design quite boring with those golf courses and those amenities (I'm not too sure if Scotland makes sense as a "happy civ"). If the Scots got some kind of castle/fortification as a unique improvement it would make them a lot more interesting, imo. After all, Scottish castles are quite symbolic and unique things.