Easy Street,
That sort of thing is a possibility. In a complex case, the Coroner can also give a "narrative verdict" that allows them to describe their reasoning and the factors involved in more detail.
Generally, I'd expect a board of inquiry to take a broader view than a coroner.
However, it's hard to see how the Coroner wouldn't be interested in the circumstances of the seat firing, as that's an undeviated part of the same chain of events. The coroner took evidence about the seemingly much less relevant Night Nurse bottle, in case that was also part of the chain of events.
I think this is a particularly complex case for the Coroner to decide. Even if the Inquest were to decide that there was evidence that the seat had been fired deliberately, a firer would have expected the parachute to deploy, and for Flt Lt Cunningham to survive, and so it might be hard to assign several of the verdicts available.
Dervish,
If interested parties are stirring the pot, I would expect the Coroner to be clear in his/her verdict, and not to be influenced. Where there is secret and arcane evidence, it's certainly possible that the Coroner would not know about a whole raft of relevant circumstances, but in this case, there don't seem to be any obvious hidden factors. While the inquest is non-adversarial, in that the Coroner questions witnesses, and there is no cross examination, there are still often going to be profoundly different views amongst the interested parties.