Ended up with the same design as Wicked Souls did.

With the new legend rules should this be legendary unless you control another permanent with the same name?

There is an argument either way.

There is indeed. I like the counterplays this currently enables, the quirky hate cards, and that it plays differently than just being legendary, so I've been keeping it as it is. I don't know though. It could be seen as a strong inconsistence. ¯_(ツ)_/¯

Random thought about blue in general -

I haven't gone through the other colors yet, but it seems like Blue has a lot of effects that bounce things back to your hand. Is this a specific archetype? I am looking at cards like Tideling of Turmoil, but I can only find the blue planeswalker as a payoff for that archetype. Furthermore, Proclaim lends itself to a slower playstyle and larger hand, and you have a lot of card draw in the set. Maybe you can have a discard or hand size archetype in ? Or perhaps shuffle proclaim out of green and make an etb/ltb flash archetype in ?

Hmmm, I never noticed the bounce theme. That's a really nice observation - there might be indeed something that could be scrambled together with that. Hand-size mechanics though, at least the kamigawa variants, were found to be not that fun to play by WotC since it encourages not playing your cards.

I've been shuffling the main mechanics (chant, distinguished, proclaim) so many times that I don't think I have the tolerance/patience/resiliency to do it again: especially for proclaim, since creating cards that make a sensible mechanics/flavor package for that mechanic is surprisingly taxing.

While straight "handsize matters" is pretty unfun, strategies that play well with large hands like discard or flash tribal could be reasonable fits and be fun. MM3 had instant control that was really fun, and you already have a card that gets back specifically instants - Alas, Fleeting Dreams. In addition, I think you can probably include a spellshaper or a card with "Discard a card: ~ can't be blocked this turn." at common and have it perform well.

So as to not comment on multiple things at once, I would probably recommend any of the following: Swanship of Alqualondë, Lady of the Sea, or Drift Apart to be bumped to a cost. Blue seems extra strong right now with all of the pseudoremoval they have.

Swanship isn't exactly a thrilling pick to begin with and Drift Apart specifically references Islands already through you could reasonably play it with only one in play.

The Swamship would likely to be the target for a modification such as the one you suggest (the common slots in blue are already filled and of the uncommon slots only is left blank) so maybe at that point it would also make sense to adjust its mana cost to be more color intensive.

Hmm, I have to delve on this.