It is the Coalition capital, there has been no indication it is the Trikru capital I think. It would be weird for Polis to be their capital when TonDC seems to have been a more important place for Trikru. They for instance settle their disputes at the Lincoln memorial.
That particular
village settles disputes at the memorial. TonDC is much smaller than Polis; it isn't a city by any means. And there's a giant tower in Polis, fashioned with all the decorations fit for a ruler to live in. It's Lexa's King's Landing, her Red Keep.
Also if TonDC is the capital, why is Becca's pod not there? Surely, for such an important artifact, they would keep it in the most important and influential area? You can clearly see in last week's episode that she lands in the ruins of what is very similar to modern day Polis.
I wouldn't say that. I think the title of Commander is something that belongs to the leader of the Coalition. So if someone not from Trikru becomes the Commander, there isn't a 'Commander' within Trikru. As for Trikru being the largest clan, the Ice Nation was big enough to be a threat to the Coalition before they joined. I think we're having to assume too much about the difference between Trikru and the Coalition for the moment. We know nothing about the previous commanders and to which clans they belonged.
Becca came down, in Polis, wearing a suit that said "Commander". With this, we can assume that the title was present
way before the Coalition happened. If Lexa was Commander before the Coalition, then it is more of a leadership position for her clan as opposed to the Coalition as a whole. She was "called" to be Heda, even before the clans were united.
For Trikru, it's part of their heritage; it's where they come from. And if Trikru weren't to have a Commander, then they wouldn't be a clan anymore. The respective clans are allowed to have leaders of their own, they just answer to Lexa. If this weren't the case, why would the Ice Queen even exist? If someone from other than Trikru becomes Heda, that's not to say they wouldn't be allowed some kind of figurehead as their own. But because they are the central clan, Heda of the Coalition and the leader of Trikru are essentially one and the same. So regardless, there would still be a leader.
For now, it seems like she only forced Ice Nation to join. I hope they go further back in time to show that the Coalition formed a bit gradually, probably due to the Becca influence.
I'm due for a series rewatch soon, but I'm like 99.8% sure they talk about her uniting
all the clans. I highly doubt that they all went along with it peacefully.