After reading Marks great write up on his Golem BOV installation and the really nice installation of a Whitey shut off, I was thinking about some possible changes to the routing I have within my YBOD for the Dil, offboard, O2 and BOV.
Here is the current setup: 
Key points:
The BOV is supplied totally indepentantly from my offboard via a GCS.
The ADV has a shut off.
Here's a proposed new configuration: 
Key points:
There is now a Whitey valve in-line with a direct feed from the O2 first stage to the solenoid - this would allow me to isolate the solenoid and retain manual O2 operation.
The GCS now feeds into a T-piece fitted into the spare end port in the manifold.
Both the Diluent and Offboard feeds go through one-way valves to prevent tanks equalising (see bottom paragraph for how I *think* this will work).
BOV fits into the new top-port of the T-Piece.
Here's how I imagine running the system:
Offboard connected but turned off, all diluent items fed from inboard cylinder, including BOV.
If there's a problem, I can switch the BOV and have access to dil for a short period of time, if I want longer, I can open the offboard, and then effectively have 10L of OC gas accessible through the BOV (assuming a 7L is carried).
By turning off the onboard, I can run all diluent sources fed from just the offboard tanks.
My questions:
This puts the manifold as a single point of failure over my existing config - how much of a risk is this in reality (considering I will still have an OC reg on the offboard, and can disconnect the GCS to make it independant again) are there any known manifold failures?
With the one way valves in the 2 dil feeds, I guess that gas will come from the tank with the highest IP to start with, once this stops delivering gas (tank empties and IP drops) I should then get gas from the lower IP first stage - if I set the offboard IP to be lower, I will automatically get a gas switch from my lean dil, to a slightly richer offboard bailout mix, whilst still maintaining all functions (wing, ADV, manual injection and BOV)?
Any comments? Am I overlooking anything obvious?!