How to repair rotting porch pt plate & cedar posts?

Any suggestions on how best to repair the massive rot all around our screen porch as shown in the attached photos, without having to completely open up the area above the posts in which the tops our contained by about a foot of very expensive clear cedar siding we relly don't want to damage? We are thinking of cutting the posts about a foot from the bottom (a couple at a time while jacking up that area with 2x6s; putting some kind of moisture barrier/flashing under the new pt plate, putting approx 12" of new 4x4 post in area that has been cut out due to rot, then sistering 2x4 cedar studs on either side of the repaired posts, wrapping the front and back of posts with 1x cedar to hide the cut marks.