Agreed Shrike. Mongoose, you also have pointed out exactly what I meant.
By having the executive branch powerful, there is no way you can have small government.
Despite the problems of the parliamentary system, I find it more adaptable than the US system. There's no pretenses about the importance of a single document more than anything else.
Yes, a constitution is a fine concept. But the problem is, it's just like a theology. You'll have literalists and "living document" types who both ignore the point: it's supposed to be a tool of the people to make their lives better, not the other way around.