Pedant alert! it's not possible to have 'more of a mandate'
Dictionary: Mandate (politics), the power granted by an electorate
The electorate didn't give that power to any party!
No they wouldn't, they would have had the largest single party vote but this would have been way under 50%, not a win!
That is an opinion not a FACT
You could have P R which excludes any party that gets less than 10% of the vote? Not sure this is a good idea but it would keep the extremists...