I think the entire discussion is a bit bizarre. If you surrender the primary then it makes not one whit of difference to anyone (except you) what sort of auxiliary you use. Each and every diver gets to go to hell in the hand basket of his or her choice, and that's the way it should be. The only merit to this discussion comes from the incredible stupidity exhibited by the diving industry's inability to standardize one of the most critical emergency procedure. That's about as dumb as it gets, akin to skydivers putting the ripcord in a different spot for each jump.
Technology changes... people cried about the return hose being removed from the aqua lungs too I'm sure. How many held off on BCs and still favor a horse collar? Belt weights or integrated? Its all the same... know your gear, understand your buddies gear... then it doesn't matter.
I think it would be more similar to letting your buddy pack your chute for you.
Then they set it to open harder or softer then you are used to.
The air source doesn't move for the diver who's equipment it is.
How about the various ways people carry thier OCTOS? Dragging them (dumbs), in a collar at their neck (Cavers), With a gate clip on a ring, in a mouth piece sheath, on an elastic ring around the mouth piece, on a plastic trident clip, on a break away, with a snap strap, on a retractor... Even if its hung in a "traditional" location it can be hug in different ways you can't get free in a panic.
If you came up in a panic yanking at my hoses your likley to get kicked away or worse until I can manage you better. If your really freaking out you get to pass out, then I'll take you back to the surface and revive you... That way we are not both in trouble.
When you get air from me you don't just TAKE it. I give it to you.
Where I get it from matters not, because I am farmiliar with MY equipement.
You as the person needing air receive it the same way from me, handed calmy but quickly.
For the instructors and people that try to stuff the reg into the other persons mouth... You can put water in thier mouth and into thier lungs if they are not ready for the reg. I really don't think this practice should be taught or encouraged.
If you tried to shove it in my mouth, your likely to get a strong negative reaction from me on that too. Just hold it out and I'll calmly take it from you and insert it myself.
Personal... shouldn't you practice some OOA drills and signals with your buddies at least once a dive trip to stay farmiliar with it?
None of this might even be an issue at that point...