All of us involved in Air Support respond to the prospect of change with some concern. From tigerfish's first post, it seems as though his response is a bit at the pessimistic end of the spectrum. Me, I oscillate.......
He is right to say that a major part of the justification for Air Support SHOULD BE in the situations it prevents simply by its existence. The reduced number of pursuits and the reduced length of pursuits is a great example, and there are lots more. I know of lots of examples where the bad-guys change their behaviour because of the existence of Air Support: so will others I feel sure.
However, before he starts blaming bean counters, he should ask himself whether all those in ASUs are doing as much as they can to keep "selling" Air Support. My experience is that, for all sorts of reasons, UEO and others vary enormously in what they do to champion their Unit and Air Support in general. Some Units trumpet their successes widely both in the police forces they support and indeed to the public. There are complex pdf Annual Reports that really demonstrate the value of Air Support with hard examples and stats designed to awaken real interest - Others do SFA. Most of us in Air Support have free time when we could be doing something to help too. If we all think it is someone else's problem, guess what - the doom mongers will be proven right.
There is a terrible approach in some ASUs: if it aint invented here, there is not a prayer of US adopting it.
I have never worked on a combined police/HEMS unit (yet). However, it is my view that they are the WAY TO GO, for many ASUs, if only a rational management process existed. The value of a rapid response (mentioned earlier) is so key to the success of many sorties. It is also true that most unit helicopters spend most of their time waiting in readiness on the ground - they are VERY expensive static displays. If you add to this that many, and my bet is most, Units will be employing some civi observers soon, then the police might as well get them "free" from the Ambulance Service.
However, it is not very likely that joint ops Units will be widely adopted if the police make their decisions and the Ambulance people makes theirs, in isolation. Central and local government departments guard jealously their own budgets, and hang the possibility of an overall benefit.
Don't be under any misapprehensions either about the ACPOs - the last thing that CCs and elevated ACPOs are thinking about at the moment is AIR SUPPORT. They will be worrying about which of the 3/4 of them is going to be the superCC of the big new shiny police force, and where they are going to build the shiny new Police HQ. Which is why there should be a bit of an Air Support lobhy going on. (Maybe there is, but I see little sign of it?)