I think you make a fair point. You're not the 1st one that I've heard making the point that the "guinea pigs"may be dealt with more harshly.
On the other hand, your PIP should have a good idea in advance of whether the proposed arrangement will be accepted or not. In practice your PIP will have discussed and negotiated with your creditors at length before you get to the voting stage. The voting stage in most cases will only be a formality.
The PIP will know how the creditors are likely to vote even before the creditors meeting is called. If he is getting feedback that the vote will be a "No" the PIP will try to keep the negotiating going until agreement is reached. If the PIP is getting feedback that the vote will be a NO, he's obviously not even going to call the meeting unless of course he's running out of time.
I guess what I'm trying to say is that it shouldn't matter if yours is one of the very first arrangements as long as you have a good PIP on board, who is competent and in control of the situation