i.e. Theres been some attempts to use the V2 boards with an Atari ST system, but some of the full 68000 implementation is missing.

Specifically, TRAPs are not handled (amongst other things).

But the point is the Vampire cards are "not naked" CPUs
The card include a lot of Amiga "chipset" and they come with a lot of Amiga "knowledge".
The cards know which areas in Amiga are ROMs and overmap their own Rom there.
The cards know which areas in Amiga are IO-areas, and handle it automatically correctly (never cache this areas, never access them out of order).
And the cards know which areas are pure memory and know which tunings they are allowed to enable for these memory regions.
 
This means the cards are designed with Amiga in mind.

As I tried to explain: 
The Vampire cards are "not just naked" CPUs.
The card in fact include some Amiga "chipset" and they come with a lot of Amiga "knowledge".
   

For example:

The cards know which areas in Amiga are ROMs and will overmap their own Rom there.

   
The cards know which areas in Amiga are IO-areas, and handle it automatically correctly (never cache this areas, never access them out of order).
   
And the cards know which areas are pure memory and know which tunings they are allowed to enable for these memory regions.  (allowed to prefetch, allowed to access out of order)
 
 
The Vampire card will do some system checking on poweron, including memory tests on Amiga memory, and also do some Amiga chipset test, and even check the checksum of the Amiga Rom before continue.
   
If you think about this then this should easy to see that you can not just plug the card into another Computer and assume it will run.
As the cards are designed for a Amiga memory layout and will actively check this Amiga and "complain" if they not find an Amiga.

Of course in theory this "Amigaawareness" could be disabled
and it would needed to build a non Amiga-aware card to run in Atari.

Let me give you more information here.
ATARI OS and ATARI programs use TRAP instruction a lot.
Its common coding practice for Programs to start with TRAP #1 and end with TRAP #1 instructions.

This all works just perfectly on Vampires.
As you might know - you can run ATARI OS / and EMUTOS and can run ATARI program perfectly on Vampire.

Maybe you even know that a number of high profile Atari coders use the V4 as the ATARI development of the choice.

Some of Arne new games like "APOLLO INVADER" have even ATARI versions - and be played on ATARI OS - on the Vampire.

I think this clearly shows that there is absolutely no instruction problem, right?

However, this is a form of hybrid Atari emulation on an Amiga platform.

Ive always wondered how much work it would be to strip all the Amiga specific bootstrap/startup mapping from the Vampire card and provide bus error support (that the Amiga doesnt use but the Atari needs) to have a more basic 68080 CPU that can slot straight in to Atari/Apple/Sun/etc machines.

Even having it hardwired as a superfast 68000 (or 010/020/030/040/060) for full plug n play compatibility would save a majority (if not all, depending on if theres any badly coded instruction timing dependant code) OS patching on the target systems. You could then have 6 types of card to cover all the 68k generations.

Im a little surprised this hasnt been looked into more, as it would increase target audience/sales somewhat I imagine.

The original poster was asking about being able to plug the card into a different 68xxx architecture/system after all.

This is what Im talking about! :)

As you know our goal is to revive Amiga.
You for sure understand that this is a big job.
We produce several different cards as accelerators for old Amigas - each model designed to fit in a typical Amiga model.
Not all Amigas are build the same - and a single card can never fit in all models.

Regarding "increase" of sales. We have over 10,000 happy Amiga customers.
What do you think about what volume do we talk here?

Its more of a whats theoretically and currently possible type of topic up till now.

As for increase in sales. Well thats up to you. :) Ive no idea when Amiga based sales will start to plateau/reach saturation level. Are you happy to leave things there when that happens, or is there another future target that could be a possibility (like discussed in my post above)?

Anything is possible.

Today already some of best ATARI developers are active V4SA users.
As far as I know they are very happy with the features the V4SA does offer them.

I think Atari market is small today

I don't think there is a lot of ST user that wan't upgrade there machine like it is done on Amiga, and Falcon more adapted for this has already CT60, TT could be perhaps better target but there is low user on this computer so huge for near nobody.
Just my point of view.

Yes I confirm for me nice small computer for Atari clone, of course it could be a bit more compatible could be nice for have more large diffusion, but with time perhaps.
The most exciting computer I have seen for long time

This is absolutely true -- the Atari ST community is very small and the attempts to keep the platform alive are nowhere near the efforts seen with the Amiga.

Hi Antony,

Using a trimmed-down V4 to upgrade a 68K Mac is an intriguing idea, however I think you'd find that emulating one on a fast x86 CPU (using ShapeShifter/SheepShaver etc) would be both faster and much cheaper. 

Of course, you'd miss out on the feeling of the Apple hardware, which is why people continue to upgrade/maintain their Amiga instead of just running WinUAE, which is many, many times faster than an Apollo V4 when run on a present-day Intel i9.

The sad thing about Hyperion's hold on AmigaOS is that it can't benefit from the Apollo MMX instructions at the OS level...if they supported them, that very old AmigaOS 3.x codebase could get a real boost.
 
  I commend Apollo for their work on the 68080 and the improvements they have made to the GCC compiler.  This is necessary to keep the platform alive.