The whole electoral system is broken anyway and needs a complete reform.
Given 3 main parties, if party A gets 40% of the vote and B and C get 30% each, party A would win the constituency. Fine so far.
However, hypothetically, if that exact result were to occur in every constituency in the country, party A could get 100% of the seats and do whatever it wanted in the country, despite having only 40% of the national vote. The other two parties, with 30% of the vote each, would have literally no representation in government.
Obviously that's extreme, but it's happening to some degree in Scotland. The SNP is set to win almost all of the seats in Scotland, having almost complete control over the Scottish parliament. That's despite the fact that it has less than 50% of the vote in most constituencies. As more power devolves to Scotland, they have more freedom to do whatever the hell they want, with no other party able to stop them (assuming it's an issue which only affects Scotland).
And then you look at the actual individual votes themselves. In the hypothetical scenario, you have 60% of the national vote which is completely ignored. They count for absolutely zip when it comes to the national representation.
As for what would be better (just a guess, as I've not studied politics outside of high school), I reckon that it should be based on % voters (x candidates per party per % point) and regional and national elections should be separate. Let parties choose individuals to represent the party in government, but have it based on the popular vote. Or have voters choose a party and a candidate they want to fill a seat in government, and have the top picks enter government.
Either way, this way would at least mean that 100% of votes would count for something, rather than be discarded if they don't happen to swing the way of the leading party in the constituency.
Local elections could then simply be based on individuals, rather than parties (potentially), and regional politicians represent the needs of their constituency to the national level politicians, rather than simply using local votes to springboard themselves into national politics.
I'd be interested to see what other people think. I'd imagine there must be some flaws in it, or else it would have been suggested a while ago (although in reality it's probably kept the same to keep old white men in power).