Hi Tilo
I like the pictures of your stand it looks very strong.
Regarding the access to the O2 shutoff, I don't know if you have completed your course yet? But the main reason for the shutoff is to allow the diver to fly the unit with a stuck open solenoid using manual O2 addition, yes the O2 tank can be turned off quickly but I think its equally important that you can reach the solenoid shutoff just as quick.
Compare this to a stuck open solenoid at depth on an Inspiration were it is very differcult to control the PO2 on the tank valve.
Regards, Al