How sweet it is to be asked such a question.
1. Yes, I use the second option if it's there. It is necessary, it's absence in a fixed cradle is a compromise.
2. It's not usually that easy, well, kindof. It would be nice if they didn't have to take their head up out of it somehow. Nothing breaks that I've seen, but I'm a rookie.
The big issue here is that these things usually suck. The worst is when they ratchet down while someone is blissfully half-asleep, jolting them severely when it gives way. This should be your main focus. Fix this problem and you'll have a winner. The ones I'm talking about are the ones that articulate via two plastic circles of triangular "gears" that radiate from a central point. They mesh together, but they are only a /\ and a \/ coming together, so the lateral (?) strength of this coupling is very limited. And it doesn't take much to have those opposing triangles slip over one another. Hence, jolting, and me appologizing.
This setup with the thing that pivots then "clamps" down is a peice of junk. Design me a good one oh saviour of my jolting woes! haha.
4.) Changes. As above, change this. I don't have a suggestion for what would be better, that's your talent, I guess. Maybe a true ratchet. *shrugs*
I would allow for opening and closing of the space between the tips of the "U"
I would allow for a dip in the table somehow so that the client's throat isn't crushed into it. The relationship b/w the cradle and the table often puts the front of their throat right on the edge of the table, choking them, not good, because often they won't complain about this unless you straight up ask them about it. Then more appologizing.
I have many more ideas for table and cradle design, but that's all you get for free.
Offers of prototypes and/or super-duper discounts on finished products would likely coax this information out of me though.
Good luck. Lemme know what you think.