Hi Moto - I'd suggest that the concept of keeping successful appraisal wells for use in a future development is out-dated. As you say it would ultimately depend on the situation, but I think your team should plan on gathering the well's information and abandoning the well at the time.
All regions of the world are still littered with appraisal wells which were suspended with a view to incorporating as part of a subsea development which never happened, and in hind sight, would never happen due to selected wellheads, in the wrong part of the field, or unsuitable for production or injection.
I well remember working for a major where the intent was to use the existing well since it would give early production to the platform. This wasn't too flawed an idea except that the platform was then located over the existing well and the jacket had to be designed and installed accordingly. Since the platform was in the north east of the field, we had to drill an additional two directional wells and all directional plans were more intricate, than if the platform were in the middle of the field.
The longer you leave the well awating use as part of the development, then the more mechanical and well integrity problems will arise. Couple this up with a tightening of abandonment procedures as the years go by and you'll see that there is very little gain in leaving the well suspended.
The P&A itself should be the same as if you were abandoning a field well at the end of its life. Meaning that you should be using the same Japex policies and government legislation for the downhole abandonment of all wells. With this being deep water, you may get your government's agreement to leave the wellhead in place- the minimum water depth is normally defined by commercial fishermen's capabilities to fish at that depth.
If you do indeed decide to leave the well for future utilisation, I'd suggest you run logs to evaluate the cement jobs behind relevant strings of casing (particularly the production casing) and emplace your cement barriers as if it were a permanent abandonment. At least if you never need the well in the future, all you need to do is sever the wellhead or in your deep water case, leave it where it is.
And - if you want to use the well for development, all you need to do is drill out the cement barriers to retrieve your conduit. (And don't put a bridge plug on top of a bridge plug!!)
Hoping that assists.......