My two penarth (old currency)
I am only in a position to ask polite questions and Keithl's post is certainly thought provoking.
If we allow air investigators carte blanche at the early stages of all investigations then does that create problems later on?
For fatal or serious injuries which might lead to fatalities
My concern would be the preservation or indeed the contamination of evidence.
Evidence is a major requirement that is always needed by the CPS when considering any allegations regarding offences that may or may not have been committed to obtain a prosecution. Without it justice might never be done or seen to be done, so will this straight away expose a conflict of interest between the various departments.
Seeking to ascertain the causation of an incident MUST have a significant priority but how high is that priority? I totally accept there will be times when 'Needs Must' but those times will be extremely rare and why should the police delay the air investigators, but let us all be aware that once air investigators start handling equipment then its evidential value rapidly deteriorates to a point where it might become valueless.
Are we all possibly guilty of being perhaps slightly naïve and maybe not thinking enough about sabotage, not by this fashionable Al Qaeda but sadly more likely by someone seeking revenge, payback or possibly someone with psychological issues that just want to create an incident.
If Mr Nutter (no relation to Nutloose) interferes with an ejection seat then they leave behind forensic evidence and this evidence would be critical if there were going to be a prosecution. If air investigators take this seat to pieces prior to a forensic team carrying out their own examination then that evidence is gone.. It is no good calling in a forensic team after the fact. They need to be bought into the investigation as soon as is practical and my thoughts are that any incident that involves fatalities or serious injuries that might become fatal should be treated as a crime scene.
The police forensic team can and should WORK hand in glove with air investigators to ensure a speedy BUT thorough investigation without any departmental rivalry. Work together and NOT against each other. Why not?
I am NOT suggesting for one milli –second one department or the other should have a priority but I am suggesting they should work TOGETHER, not sitting in on interviews or wasting each others time.
No instead why not sit down, discuss what the Air Investigators need to do and in what priority, then listen to a forensic team say what they need to do to obtain evidence? Work TOGETHER and NOT against each other, it can be done and surely it would be quicker to work together as opposed to bicker, argue and fight against each other.. The LAST thing either team would want is OUTSIDE INTERFERENCE.. 
Nudge nudge wink wink we know who I mean.
Regarding Point 7
I would much prefer the military to keep minor crimes in house and not even involve the police, let the military police investigate and let them decide if the civil police need to be informed. I am asking myself why they should be told about minor transgressions.
Hopefully my witterings make an okum of sense and the spelling miss steaks have all been salted and peppered (I actually accidentally typed slated which I thought funny)
Best wishes to one and all
John