Allow spectators to watch

[Khoo1]

As for cheating, if anyone wanted to cheat, all they had to do is subscribe to 2 BGA accounts, play both accounts against each other and full view of the game. BGA would be rich

Cheating with the consent of the other players at the table is something.
(In fact, if there was no ELO, I would see no reason consider it "really cheating". With ELO, that's more arguable.)
Having the ability to open a second browser (or the same browser in private mode) to watch the game as a spectator and "fake" being clever by always interpreting correctly the hints given to you is much worse. And I believe it's what BGA was trying to prevent here.

[By the way, creating an alternative account to play against yourself and increase your ranking is one of the very few things forbidden by the rules of BGA. While they don't have easy ways to enforce it, it would not be just cheating at Hanabi, it would make you banned if discovered.]

No ELO is a good suggestion.
It would be difficult to determine game level to offer to players.
Also difficult for players to find players of similar understanding ( to some extend )
I am alright with dropping of ELO on Hanabi but I doubt it would be executed.

Best way to learn is to play yourself, what's the worst that's gonna happen.. Oh no!!! I lost a game. Big whoop.

Learning through mistakes is how you play this game, especially for beginners. Then you'll get the proper taste of victory when it finally comes.

Training mode is available for learners.

I am in support of Table owner / starter to set the table: Available for Spectator viewing: none / player / full
"Player" would mean, Spectator has to choose the view of one of the player.

But I do not work at BGA so do not expect this anytime.... at all LOL