What would you be able to set the diluent to, with regards to the O2 percentage? (with the blue battery, a minimum of 16% is allowed)
16%. The reason for this is the risk of hypoxia on OC on shallow depths. Breathing a gas <16% on surface may be hazardous.
Could the new lungs be fitted onto the Poseidon Rebreather BC's?
No, not without modification which would invalidate the CE approval
Would it matter if the customer sends either a Blue battery, or a Green battery for the upgrade process – are both upgradable?
Any battery will be upgraded as long as it works.
Could the White battery be used on another machine that has not been upgraded?
Yes, but you can not enable 60m functionality
What exactly needs to be upgraded on the e-modules?
Hardware, nothing that a distributor/dealer or user can do
What will happen if a 60m battery is used in a non 60m upgraded emodule?
Nothing except that you can not dive to 60m, only 48m.
Can the old counterlungs be converted/used