Can you still use Weaken Resolve from a chimera? It would seem not:

Pg. 67 says a psyker must have LoS to his target, and that an embarked psyker cannot target anything outside his transport.

The Fire Points rule on Pg. 78 says that you may use Witchfires and Psychic Shooting attacks only out of a fire point.

As weaken resolve is neither of those types of powers, do you have to disembark now to use it?