Seattle is a tough deal, for a car that is looking to have grip year round
I am fortunate to live in an area where I can run my "Summer" wheels, from April to October. Little rain here/there, but don't DD my ride, so not a big deal for me.
As for suspension... you are building to take corners, but will not be able to really get the most of it, on an A/S tire
To me, it looks like you should consider the alternate set of wheels thing, to justify the upgrades of suspension.