Maester Lomys reads: Any Phase: Kneel Maester Lomys and discard 1 power each from any number of characters you control to have each of those characters gain "cannot be killed" until the end of the phase.
Wildfire Assault Reads: When revealed, each player chooses up to 3 of his or her characters. All characters not chosen are killed (cannot be saved).
My Question is could you use Maester Lomys at the beginning of the phase (even if you need to use Dragonstone Port to do so) discarding a power off of character A, & B. Play Wildfire Assault as your plot (choosing Characters C, D, & E) effectively retaining 5 characters since you are not saving only they cannot be killed. Also since Wildfire Assault does not target characters to die (only to not be killed) you are not making any illegal targets.
Does this work?