why not SCTP?
Multipath TCP sounds like an interesting thing. It however tries to solve a problem which has already been solved.
SCTP is available since over 10 years and has multipath built into its core. Its made for robustness so you can add / remove links as you want and the upper layer connection will not go down. So why not use an industry standard protocol which has been implemented in every major operating system and which has proven its working well already?