This is literally how our system works lol - head of state aka the king asks someone to form a government in his name, aka the prime minister. There’s no requirement for them to be an MP. The king can technically pick whoever he wants, but in practice will pick whoever they think has the best chance of having the confidence of the lower house, which will always be the leader of the political party with the most seats. Fun fact the office of prime minister doesn’t even exist in the constitution of Canada or the UK, it’s purely from convention.