MDW - While I agree with the rest of your points regarding streamlining. I don’t believe we have beaten the integrated octo topic to death as it eliminates an extra hose and removes the posibility of an Octo dangling or tangle with environment.
Also consideration as to the need to deploy your primary second stage to an OOA buddy may inhibit the choice of 90 deg fittings. This isn’t to say a 90 couldn’t be used but swivel fittings and long hose may also serve well.