Auto Seige T/O

Much like Tourneys, Seiges are not a "one-on-one" event: there's a queue and all those other players are waiting.

In such setups, I think the T/O should be automatic: it is unfair for a player to stall the queue, even out of kindness towards their current opponent: its an unkindness to their future opponent(s). (Given that you've got to be 'unkind' to at least one or other, then the player who has already failed their timing commitment seems the obvious choice).

Also consider the case of two abandoned accounts: with no automatic T/O: that seige stalls forever without an auto T/O.

I agree, and I think the next game in the queue should auto-start too.