I dont understand why D19 is a problem for PPM. That pin was specifacally chosen because it offers interrrupt (for PPM) and it could also be used for spektrum satellite RX (Serial connection)
If you look in the Preter 1.7 code you will find that D19 is defined for PPM sum RX:
#define PPM_PIN_INTERRUPT attachInterrupt(4, rxInt, RISING); //PIN 19
Now, who is gonna make Spektrum sat happen for MultiWii?...
I seriously would like to use a sat for Mega versions (I wont come near the 600-1000 Meter range limit for for spektrum sats and parkflyer RX´s)