The further I dig the more RUST opinions please

[va944]

I knew there was rust when I bought it but I did not realize that PO had installed knew rocker over completely rusted out lower pillar. It is solid up where it attaches and where the door attaches but as I peeled back the rusted floor, footwell, and floor support I quickly realized that down where they tie together it is gone. Is there any way to replace that part of pillar without removing destroying a good rocker? Or other suggestions please.