The listed supposed conflicts of interest mostly aren't any clearer than the baseline assumption "ex generals will generally favour more defence spending" which anyone with more than two brain cells should already be working on.

How is an General Everard being a patron of an armed forces charity, a software company enhancing onboarding experiences, a skills training company or even an "informal network of strategic thinkers" who write blogs likely to influence his defence spending views more than being a general?

It's not like it's standard journalistic practice to provide the entire resume of any other type of commentator.