Board Game Arena

But, this does NOT prevent two things:

1) Intentionally causing this to happen to deny the winning arena points to the player who would win if the game were completed,

and

2) Allowing the losing player to do this intentionally, not caring about losing the arena points, because that player instead prefers to not lose the Elo, which will be avoided when the game gets converted to friendly mode.

Also not sure how a player could do what you describe, you have to take your Arena turns in order, they cannot be tanking in a game they've lost while playing games they're winning.

That is very easy to do. Open each game in a seperate window and youn can just keep on playing it. Only when you reload the page comes the message that you have to play this other game first. I sometimes let a specific game open because I want to finish it quickly and not always have to play my turn on each other turn based game first.