These things take time. And the final bill will have quite a few amendments based on evidence weighed, in-depth discussions, what witnesses say, constitutionality of changes being proposed etc.
For example, if something that is not constitutional is included, it could easily be challenged and the movement of the bill could even be frozen/derailed - until the court gives its verdict. Therefore, this will be carefully debated and controversial clauses that can be challenged in the Supreme Court will only add to the delays/complications - which they would not want, logically speaking.
We have already seen what happened with the Nadon appointment and other SC rulings. The highest court of the land is expected to deliver justice with impartiality - regardless of Cons, NDP, Liberals or whoever.... no messing around there !