HEY! That TICKLES!
Crazy, that makes the William Hamleigh: Black Master Builder that much more powerful. Not only do you get to block a spot and get it cheaper, you also get to place your pawn later in the Builder Track. That's a must get power in a 4/5 player game imho.
Maybe. Powerful, but luck-dependent.
1) Obviously less game-changing if he comes out in a late turn. William Hamleigh on turn 5 or 6? I'll pass. Turn 3 or 4 even, depending on what other opportunities are out there.
2) The odds of his coming out early in the master builder draw are small. And if he comes out later he's not so useful. Compare that with other privileges where you have a guaranteed benefit every turn.