HISTORICAL JUSTIFICATION:
It may seem odd that I chose to start the Celts in Ireland, when it is on the Continent that they are most known during the ancient period. There are several reasons for this, and it is not as historically inaccurate as it might first appear.
First, the reasoning: this was of necessity. Starting the Celts in Gaul or Iberia made it virtually impossible for even a human player to survive. The way the medieval civs spawn would virtually necessitate even a human player moving their capital to Ireland in order to survive. As there is a penalty for moving your capital, I figured it was best simply to start the Celts where they would eventually need to be centered.
Besides that, starting them in Switzerland virtually insured prevention of the Roman Empire from forming. For this reason, independent and barbarian city spawns have been used on the Continent (with Gallic Warriors) to reflect their presence as independent Celtic tribes. The English (Saxons) are not started in Germany and expected to recreate the migration to Britain, nor the Franks started east of the Rhine and expected to invade Gaul, so why make the Celts migrate from Switzerland to Gaul to Iberia and then the Isles? In reality, the only major Continental population of Celts is in Brittany, which is not a remnant of Gaul, but a recolonization back from Britain (hence the name, "Bretagne").
When the Celts spawn, 820BC, they were indeed present not only on the Continent, but Ireland and Britain as well. The fact that they are most known on the Continent during the ancient period is a reflection on the limited perspective of our surviving sources' authors more than actual Celtic presence in a particular place outside Roman and Greek borders. Setting the capital in Ireland marks a shift in focus of narrative location rather than an idiosyncrasy. Indeed, some historians argue that proto-Celts and Basques comprise Europe's aboriginal peoples, and some geneticists studying the population in southern and western Ireland (as well as the Basque country) reveal a pattern of initial migration - in other words, the people there now are direct descendants of the original people to settle those locations, even in the face of numerous invasions and migrations throughout the rest of the continent.
Ireland is today the only free and independent Celtic country. Brian Boroimhe's consolidation of power (such as it was) as Árd Rí Éireann (High King) was as close as any collection of Celtic kingdoms or tribes came to cultural and political unification until Ireland's independence in the modern age. There was some Scottish unification, but this was outlived by Irish kingdoms' independence and Scotland was the result of Irish (Gaelic) expansion into northern Britain in the wake of Roman withdrawal from the south in the first place. The selection of Tara, the seat of Ireland's High Kingship, as the Celtic capital is therefore a symbolic starting point for someone trying to unify the Celts and keep them unconquered into the present day. After all, it is London that is most associated with the position of being England's capital, even though Winchester should be the capital in the early stages to maintain historical accuracy.
I have tried not to make concessions for the Celts that Rhye himself did not make for at least one (and preferably two or three) other civilzation(s). Far from overpowering my favorite civ, I have actually been fairly strict and therefore many may find that playing the Celts is harder than other civs both in terms of UHVs and competition with their neighbors. In the end, the Celts were not able to survive English (and others') expansion due to disunity, and only "respawned" as a politically independent entity in the early twentieth century. Trying to buck history should be hard. Other "unconsolidated" civs were given a place in RFC (the Vikings, the Russians, and others), so it's not that outrageous that the Celts could be as well. All civs were given two UHVs they achieved in history and one they never managed to...this is true for the Celts as well...the one they never managed to accomplish amounts to surviving past the Battle of the Boyne in 1690 (1700 to achieve the UHV) without losing any cities to the Romans, Vikings or English. The others, sacking Rome by 410 and colonizing the British Isles, Gaul and northern Spain reflect actual historical events.
).
