I guess if you're a Protestant and meet certain conditions- do you see how this is garbage already? Also it's not a codified constitution. It can be mangled like any other law. Your entire system needs rebuilding. It's why we made our system the way we did. Yours is busted.
England was protestant and the king was Catholic so arming specifically protestants was one of the many ways to assure he wouldn't attempt to lean on people to get the nation's religion changed. It also limited his own power considerably, and it also acknowledged that an armed populace was a good deterrent to unwanted change by the government. It also was a codified constitution, 'bill of rights' was just the name given to such at the time (like America's 'bill of rights', inspired by the UK's, becoming apart of what is now called 'The Constitution'). But like I mentioned before, because supreme power is in parliament, it's easy to change them. America can alter its constitution too, it's not untouchable, it's just a more involved process requiring both the proposal of congress and the assent of the senate. See:
18th amendment.
I also agree it needs repair, but your system was built as a mirror to it, it's just while power became evenly distributed in yours, ours got consolidated into one of the bodies. We had an executive, and two legislature bodies with their respective roles. (Whilst we lacked a supreme court, so did America to begin with, as there wasn't one to borrow; we would eventually create one, but since doing so would require Parliament sacrificing some powers, it's pretty much powerless.) To show what I mean:
President = King (UK king is purely ceremonial, no actual power in practice, some power in theory - the US president has (and had, even in 1783) more power.)
Congress = Parliament (Supremacy after the glorious revolution and English civil war (
became a republic for a little while) with the combined powers of US senate + presidency + congress. Can propose laws, implement taxes, dictates military, etcetera. 'Royal assent' is just ceremonial.)
Senate = House of Lords (Members chosen by parties in parliament with some leftover hereditary seats given to bishops. Can't veto laws, only send them back to parliament for certain alterations, but will ultimately have to assent to their passing even if the alterations aren't entirely met)
This isn't to insult or belittle, it's more to point out that your system works because it was a fresh copy of a system that had worked for centuries. What happened to the UK/England in the long-term is somewhat of a cautionary tale for when the distribution of power and allocation of authority gets ignored, and the potential ramifications on the country's future. If you have autism and like history, try going down the rabbit hole of the English civil war and subsequent glorious revolution. You had a country divided on faith/ideology, an executive trying to skirt the role of the legislature without doing technically breaching the law, and sparking it by arresting members of said legislature who were colluding with an invading army.
I'm sure there's a way you can interpret that to make it sound vaguely familiar 
TLDR: Keep power divided between the senate, congress and president with centralising too much power in one or else you'll gradually lose your rights (or see them taken away faster, depending on how you view things currently). The UK's system and it's similar to America's indicates the former can be fixed but also that the latter could become just broken in unfortunate circumstances.
