Probably not. A dedicated MITM attacker could simply strip off the MultiPath TCP options from the initial connection, so it would act merely as a regular TCP co

Probably not. A dedicated MITM attacker could simply strip off the MultiPath TCP options from the initial connection, so it would act merely as a regular TCP connection in that case. Good crypto is a much better solution to minimizing the likelihood of a MITM attack. MultiPath TCP is design to provide speed, reliability, and mobility of TCP connections.