Arcbound Ravager and Shortcuts
You have to specify the order of sacrifice when asked to, and you still have to propose a shortcut that involves sacrificing all your artifacts, as originally proposed.

Since the Ravager only allows you to sacrifice one artifact per activation, the proposal of "I sacrifice all of my artifacts to Arcbound Ravager" was technically not legal in the first place. From the CompRules:


  719.2a At any point in the game, the player with priority may suggest a shortcut by describing a sequence of game choices, for all players, that may be legally taken based on the current game state and the predictable results of the sequence of choices. 


Of course, if the order of sacrifice didn't matter to any player, it would still be an acceptable proposal. However, since it did matter, your opponent can force you to spell out the order of sacrifice. You may not modify your play as a reaction to your opponent asking about the order of sacrifice. From the Tournament Rules:


  4.3 Out-of-Order Sequencing
  
  All actions taken must be legal if they were executed in the correct order, and any opponent can ask the player to do the actions in the correct sequence so that he or she can respond at the appropriate time (at which point players
  will not be held to any still-pending actions).
  
  An out-of-order sequence must not result in a player prematurely gaining information which could reasonably affect decisions made later in that sequence.
  
  Players may not try to use opponent's reactions to some portion of an out-of-order sequence to see if he or she should modify actions or try to take additional ones.


While the examples for out of order sequencing don't include one similar to your scenario, combining individual actions that can't be combined arguably also fall under that rule.