If changing personel is NOT an option, then I go right after WHOM, maybe a brighter AC version, but right after them. Here's why:
WHOM is not "home" to anywhere. Listen to them for two hours and you could think you're listening to a NH radio station. That is their achilles heel. Attack it. Become Portland's Lite. If you want to be corny (please don't) and use a "lighthouse" brand. Better yet, you could probably just keep Coast and change the positioning brand; imaging, etc. Coast is a geographical positioner not a formatic one.
Tim and Eva will then work nicely and would immediately be better than the current morning programming on WHOM. Ethan is fine for this format; even perfect. Move Randi back over and have Alisha voice track POR. She already has a presence on that station and it would make a lot more sense.
You're already competing in the W25-54 demo to begin with, so there's not a radical change there. You have Q97 on one side of you and WHOM on the other side. If you are not willing to change the personel on the station, which is what this whole premise is being based on, you have to go after WHOM and not the Q. WHOM is vulnerable because of the reason I mentioned; the Q is not and you have the personal in place to do it.
Have I nailed it yet?