"the Constitution is not silly putty, as if it could be altered lightly."Absolutely. Doing that is when one does end up with a dog's breakfast -- like a constitution that enshrines equal protection, and then expressly denies equal protection to, say, partners in same-sex conjugal relationships.
There's always going to be something of that in a constitution. The Canadian constitution, for instance, grants express rights in various matters (e.g. education) to speakers of English and French -- but not of Hindi.
More problematically, the 1867 constitution, which continues under the 1982 constitution, grants express rights to protestants and RCers as regards separate publicly funded educational systems in various provinces -- but not to Muslims or Wiccans or anybody else.
The provision in question was absolutely essential to the pact that was the basis for the formation of Canada: a pact between two
peoples, with guarantees of
collective rights to minority
groups.
But when looked at from the modern perspective of
individual rights, and especially the very strong guarantees of equality -- equal benefit of the law -- in the Canadian constitution, that provision is a big problem. In fact, the UN Human Rights Committee has found Canada to be in violation of international rights instruments because of this situation:
http://www.un.org/documents/ga/docs/55/a5540vol2.pdf-- RCers and protestants who are minorities in some provinces have publicly funded separate schools (they may not discriminate in admissions), but Muslims, Jews, etc., receive no public funding for their schools.
Essentially, the constitutional guarantee is an anachronism in a multicultural, tolerant society which values and fiercely protects both individual rights and freedoms and collective cultural and religious rights. In Canada in the 21st century, no religious minorities need publicly funded schools to protect their religious freedom or preserve their identity.
But it is a little high-handed for an international body to rule against the fundamental bargain struck by the founding peoples of a nation, nonetheless. The recognition of collective rights expressed in that bargain, and the culture that grew out of it, are, after all, what made Canada the tolerant and multicultural society and exemplar of modernity that it now is.
Of course the proper solution, now, is to do away with the guarantees of funding for *any* religious groups. The Constitution is a living tree, and that dead wood absolutely needs to be removed.
With the Catholic Defence League lurking under every rock, in particular, that isn't likely to happen anytime soon. Although in Newfoundland, which had previously had a completely denomination-based schools system (11 different and completely separate systems), a referendum was held that resulted in a constitutional amendment in 1997 abolishing the entire denominational structure in favour of a single public system. Small population and particular events (scandals about abuse in denominational schools) made this possible.
Anyhow, that's how I, an admitted outsider, would see your constitutional citizenship requirement for the office of president: dead wood, and inconsistent with the fundamental values otherwise expressed in that constitution. I do recognize the special situation that results from the fact that this office is the head of state, but even then I don't see the requirement as consistent with a modern, tolerant, multicultural state that values equality.