Thank you,
I did a bit of testing and I can tell you that the last MechJeb Dev build that works is MechJeb2-2.6.1.0-741 after that the Dev builds stopped playing nice.
Since MAS is intended to be the replacement/successor for RPM is it possible for you and Sarbian to collaborate to ensure that MechJeb will always be compatible?
I am not very familiar with coding but I know enough that is can be very labour intensive so thank you for all the hard work and time that you mod creators put in.