1) You can recover from a replay if you're playing a friend. But if you're playing a 1v1, you can't expect your opponent to just wait for you to come back, since they have no idea how long it will take you to return.

2) There are technical limitations/trade-offs that have been discussed on this sub many times. I can't remember exactly which threads I read these from so I'm just going from what I remember. Basically, most MOBA's save the game state at some central server. For SC2, the game is run by having each player issue certain commands, and earlier commands eventually lead into the later commands. This is why you can't just skip to the middle of a replay, the computer needs to process all earlier commands in order to "know" what happens later. The advantage of this is small replay file sizes and the ability to play on a slower connection. All of this is saved on your computer, not a central server. So if you wanted to spectate a game, you'd have to start from the very beginning of the game and the spectator would need to grab the information from one of the players' computers.

The other issue with delay is that a 2-3 or even 5 minute delay is fine for a MOBA. For SC2, a 5 minute delay can still reveal valuable information. A ninja expand or hidden tech may not be scouted for 5+ minutes. Some tech switches take several minutes long, especially if you're terran. By then, the game could very well be over, since SC2 games are generally much shorter than the average MOBA game.

3) The wider array of pings would be nice for team games, though I would imagine there would be a big hotkey issue. SC2 uses a lot more hotkeys so a lot of hotkey space is already taken up. Dragging would be impossible since you need to box units, something you don't need to do in a MOBA.