Change the process that when a Prime Minister resigns,a general election is held

Too often, a resignation as a PM means very little, as the MP still holds sway within their own party and know that many of the things they’ve started cannot be changed. If there were the looming possibility of another party having one of their MPs as a PM, this would stop abrupt resignations as this would need to be factored in. This would also allow the public a chance to look at different views and have a vote on who is running the country, rather than a small section of MPs voting on this.