Some of us do not live on the internet.
As for a contingency plan, it's pretty freakin' simple:
1) If the site is well known (Pt Lobos type dives), a "rally point" can be set as part of the pre-dive brief. A search would be to return along the route of travel toward the rally point for the "forward" diver and a brief search ahead for the "rearward" diver, then turn and head for the rally point.
2) If the site is known, items such as the navigation and major landmarks are briefed unless it falls under 1. Even new sites get briefed based on bathymetry if available.
3) If diving from a boat that is anchored, the rally point is automatically at the anchor unless some reason precludes it (anchor is deep, started deep and worked the way up the reef).
Bottom line is this: in a bunch of OW scooter tech diving, I have yet to see a situation that would call for a 100' spool. Have fun with 40 seconds of possible buddy searching in any direction while you waste time with the spool.
AG taught us to be thinking divers. The more I read from you, the more I think you have lost that and so blindly follow the decrees that there is no room for deviation even when the procedure you are following does not make sense in the context.
When I penetrate a wreck (or may accidentally penetrate, say on an exterior survey dive or dive one on a new wreck), I carry a separate safety spool from my pre-rigged SMB. If I were to dive thirds in OW tech diving, I would carry a separate safety spool. When I go for some cave training, I will have a safety spool and no SMB unless for some odd reason one would be useful at the entrance.
When I'm out on the scooter, the safety spool becomes useless, and so changes in protocol are required -- set the rally point, brief contingencies, and remain a thinking diver no matter what happens.
Have I been split up from teammates on scooter tech dives? Yes.
What happened? Well, since we all knew the navigation, the lead diver(s) returned on the path travelled and met up with the behind diver(s) as they scootered up.
Have some of our 2x team of 2 (the way to dive 4 people to a "team") been split into two separate teams of 2 each on scooter tech dives? Yes.
What happened? The pre-brief was "in the event of a split up, each primary team will continue the dive as a team of 2; we'll try to meet at Lone Metridium on the way in." That's what we did, and both teams made it back safe and sound as teams of two.
Have I been split up from teammates in low visibility OW tech dives with deco remaining? Yes.
What happened? We were returning to Whaler's Cove in 5-10' green cruddy vis (30-20' depth). My scooter decided it was time for the battery to stop. I instantly fell behind the other teammates and became "lost." Navigationally, I knew where I was. I continued to swim slowly toward the boat ramp, and when I hit 20' I switched to my O2. I stayed there for the deco since they had scooters and I was a better target if I wasn't moving. They continued to search for me, and I swam in slow circles looking for them/their lights. 20 minutes of deco later, I surfaced. They surfaced about 100 feet away a minute or two later. We reunited on the surface.
It only takes a second to get split up on a 1/2 usable tech dive, especially with scooters. In all those situations, a safety spool would have been useless. But you know what was nice?
That pre-rigged SMB I shot while I was decoing all by myself.
Think about what you are doing...and why.
