The great benefit of FPTP, from the point of view of a hostile power, is that it allows much easier manipulation of elections to get the desired result - an actual majority of votes is not required.
Hence Donald Trump was elected with 3 million fewer votes than Hillary Clinton in 2016 and Boris Johnson got a "landslide" 80 seat majority with most voters voting against the Conservatives in 2019.
FPTP might be good enough for a puppet state like Belarus, but surely it should never be tolerated in a country aiming to be recognised as a liberal democracy?