John_B
Grasshopper
Great points, as always.I think Larry nailed the biggest concern in this particular case.
A couple of other things to be aware of -- The inflator hoses for octo/inflator units are different from standard inflator hoses. Therefore, if you are somewhere exotic and the hose to your unit fails, you may not be able to replace it. You also won't be able to use your regulator on anybody else's BC, unless you change out that hose.
Second, if you DO use an octo/inflator, it will help a lot if you put a longer than standard hose on your primary regulator. You are going to donate it, and the standard 24" hose is VERY short for air-sharing.
Whatever system you end up going with, make sure you practice with it. The time to discover any awkwardness or learning curve on using a piece of equipment is not DURING an emergency.
I'm not really a big fan of the Air2, etc. but if I had one I'd make absolutely sure I had a spare hose that fit the model I had in my SaD kit -- before I took it on any trips.
The other thing I'd do is to put my primary reg on a 40" hose (either the new flexible Miflex hoses or on a 90° elbow*, or maybe both) and route it under my right arm. That's the minimum length I'd want for an air share. YMMV.
* Note: Stay away from the 360° swivels as they have a tendency to fail and several models have been recalled.