When I had mine on the transom the straps stopping it breaking and falling overboard would have taken longer to undo than what I propose to do this time.
The outboard bracket is above the top of the transom when raised. Putting the outboard on is just a matter of undoing the two clamps and one strap at the bottom of the leg and turning it round and tightening the two clamps again.
Shouldn't take any more than 30-40secs.
If you are that close to something hard and drifting towards my first thought would be anchor, not outboard. At least the anchor is more likely to hold and give time to sort everything out and is quicker to deploy.
From my experience there is no guarantee the aux will start first time anyway.
Its all a compromise of what will fit and is practicable, personally I wish I had enough money to buy and run twins and I wouldn't need an aux........