I read Fencer's points the last time this came up and I found that each was arguable rather than definitive. Now, having experienced autopass at GoldToken, I'm even more certain that the reasons given against it, from the point of view of the players, are spurious. For instance, there can indeed be startling changes to the board and game position but that's in no way a problem. And yes, messaging does suffer during the autopass period, but BK wouldn't suffer the loss of messages that GT does because BK's messages are always visible.

I do accept that there's a technical difficulty with Backgammon, though. At GoldToken the dice are rolled at the first opportunity. For instance you can make a move and submit it then go back to the game page and the opponent's dice have already been rolled, even though the person may not be online. Here the dice are rolled at the last moment, ie. when the player visits the page. That's a fundamental difference that would need to be addressed before autopass could be added to the gammons.

In chess and other games the conditional moves facility that you're talking about is different from the Backgamon autopass and is possibly even more difficult. The simple case of my-move, his-move, my-move, his-move may be feasible but I imagine it wouldn't really be very effective; as soon as it was available you'd be wanting to add choices at each move thus creating a tree structure. I believe that that would greatly add to the complexity of the mechanism and the user interface required, making it a very expensive feature in terms of Fencer-hours per site improvement.