They are PIC and you simply observe and decide.
The problem is that in doing so (letting them be PIC) one is stating that one is happy with their ability to be PIC and in the circumstances described this could be described as "jumping the gun" or perhaps a bit reckless is one did not know the capabilities of the person being so authorised.
Genghis,
I think that you need to re-read my post. I said quite clearly that the person checking should confirm that the new member meets the syndicate requirments. As you say - your aircraft, your requirements.
However, since it is clear that you take pride in and value this particular aircraft type so as is your right, you require something other than basic PPL skills from new members. It would be a good investment on the part of the syndicate to invest some time and money in putting in place someone who can provide training and checking to both current and future members.
You are quite right to believe that wheeling in some instructor from an FTO to do a checkout as a money making exercise on their part will not help at all. They will have no interest in your aircraft and will simply do what is required to get the payout and cover their rear end.
What is needed is for the syndicate to sit down and decide how to attract a suitable instructor into the sydicate (perhaps honorary non- paying posiiton that permits them to fly the aircraft) or for one of the current members to become an instructor.
As you will know from your previous experience -
Mr A checks out an aircraft and says it it airworthy. Is it?
Mr A gets the appropriate piece of paper which says they can say it is airworthy and then it is.
At the moment you are doing the equivalent of building an aircraft with no engineering oversight. Your aircraft, your rules...........but would you with one of your former hats on see that as a healthy way to proceed?
It is very different from taking on a completed aircraft with the required paperwork isn't it!!
If you have an interesting aircraft then I can't see how you would have a problem finding an appropriate friendly instructor to help you out not just for now but in the long term.