In my opinion - the unwritten constitution attitude of judges (I remember one justice on the supreme court mentioning that it did not matter what the constitution actually said) these days is a big problem because in 1982 we went from from a largely unwritten constitution to a written one. With an unwritten constitution - the supreme court can make a ruling that something is "unconstitutional" and the parliament comes back with a new law making it "constitutional" (i.e. written). With a written constitution - which in many cases is very very difficult (almost impossible), you can get activist judges (left or right) making decisions about constitutionality of an issue and basically writing law - which is not their mandate. Now with the Canadian constitution (written) there are several areas that are left open for the courts to decide - one is extending equal rights (wording of our constitution gives leeway to the courts using discretion on extending "equal rights" (use of word particularly - in conjunction with a list of non-negotiable rights. Other things like transfer payments is also part of constitution (but not the actual formula) - also leaves it in the discretion of the courts if they think a formula is against the will of the constitution (i.e. a transfer formula of zero). When a constitution is written, judges should be more conservative in what they deem unconstitutional since they start moving into the domain that we have a parliament for - but creating laws that are almost impossible to change.
First of all, Canada has had a constitution since confederation in the form of what was formerly known as the BNA Act. Second of all, the living tree doctrine of constitutional interpretation that you're describing has been around a lot longer than the constitution of 1982. In fact, it dates back to the 1929 persons case (allowing women to sit in the Senate). Canadian society is not static - it is dynamic and ever-changing. The constitution must be interpretted given that fact. We don't live our lives and we don't have the same values as Canadians in 1867 or 1982 - we shouldn't need a constitutional amendment every couple years to keep an archaic document relevant when the top judges in the country, as (by convention) chosen by our elected leader can expand on what is already written in it. While often the decisions of "activist judges" can be controversial, I cannot think of one in Canadian history that hasn't been over time accepted or even held up proudly as an important moment in our evolution as an inclusive democratic society. If the decision of the Supreme Court was really that offensive, the democratically elected legislatures of this country could simply amend the constitution to remedy the problem. That they never have suggests to me that the Supreme Court is extremely responsible with the powers it has been entrusted with. Governments also have the ability to invoke section 33 of the Charter if the court finds it in violation of sections 2, and 7-15 of the Charter.
There are too many competing forces and interests in this country (the federal government, the provincial governments, First Nations, minority language groups, etc.) to allow for absolute Parliamentary supremacy.
But does the PM have the right to replace a democratically elected GG? Like it or not, but strictly speaking, the GG/Monarchy picks the PM, and commands the military. Neither are purely ceremonial, but are treated that way. In a crisis, all the velvet gets ripped away and the cold hard truth is that the PM is the PM at the pleasure of the head of state. I'm still waiting for an example of an elected, non-political head of state. The problem is that once you give that person democratic legitimacy, they feel a greater freedom to use the very real power they hold in their hands.
The President of Ireland is elected by popular vote. Candidates for President must be nominated by a group of at least 20 members of the Oireachtas (their parliament), or at least 4 city or country councils, or by themselves if they are the incumbent. Elections for President occur every 7 years, and Presidents are only allowed to stay in office for two terms (14 years in total). The constitution gives the President certain powers, but the President rarely if ever uses them. This seems, however, to be because of an anomoly in the constitution - the powers given to the President are worded slightly differently in the Irish and English language versions of the constitution. When a conflict occurs between the two versions, the Irish version of the text has the final say - in this case, the Irish language part can be interpretted many ways and so far no President has decided to force the issue to the courts. While Presidents are usually affiliated with one of the political parties and candidates run under party banners, the position isn't overly politicized. Parties often endorse another party's candidate, and often one candidate runs unopposed (making an election unnecessary).
When it comes to a hypothetically elected GG in Canada, it must be remembered that the primary role of the GG is to represent the monarch in this country, not strictly to represent the people or the nation (though s/he does both). If we were to elect the GG, I'd imagine that instead of directly electing a candidate to the position, the results of the election would be taken to the monarch as a recommendation. The power to appoint and dismiss the GG would have to remain with the Crown, but s/he would need the people's consent to do so. Frankly, I don't see the point in electing a functionally powerless representative of a functionally powerless figurehead. It'd be a huge waste of money to hold a national campaign and election every five years (and, I would assume, 10 seperate provincial elections every year for the post of LG). If we should be pushing for democratic reform at all, our attentions for now should remain with the Senate, which actually has power and occassionally uses it (whether this is in the form of an elected senate, or in abolishing it all together, which I would favour). I wouldn't mind seeing the PM's recommendation for GG approved first by our democratically elected representatives in the House of Commons before going to the monarch though.