I know this is, at best, a distant solution, but is it possible?
I would guess that it is only selectively possible. If there are resistant specimens among a species one might be able to identify that genetic trait and cross-breed it into new individuals. NOTHING can be done for existing specimens genetically that way. Even if they did identify resistant alleles, they would still have to distribute that trait. By pollen seeding? Who knows, there are a lot of trees out there and that is a lot of pollen (in tonnage). Finally, propoagating many native plants by seed is no picnic. The research is very primitive. I am actually doing a little on plant propagation in my spare opportunistic moments that improve the ability to reintroduce local stock in the field. I have an air-layering process for manzanita that is not in the literature and am fooling around with charate instead of fire-scarification on manzanita seed.
Another tack might be to identify a parasite of the disease (a bacteria or virus that would consume or infect phytophthora alone) or something that inhibits its action in the host by more successfully occupuying the niche in advance. Both strike me as high-risk options.
It's bad. It could have been prevented. The system needs to change before it happens again. If we can instute that change we may have more success at finding solutions. That's the real message here.
Yes it's possible, I'd be surprized if someone isn't working on it right now.