It would help if you explicitly stated what you did want to the application to do. I guess you want 8 or more channels to controlled directly from the transmitter when the the receiver has a good signal, but switch some or all of the channels into preset failsafe values when the PPM signal is invalid.
If that is the case then you may want to try using ServoDecode running in a controller that has two (or more ) 16 bit counters, such as the teensy. In this configuration, the decode would run off on timer and the servos off another. I wonder if someone has already tried this to see if the two timer interrupts would cause any noticeable jitter.
Michael