PCI-Express on SATA or SATA on PCI-Express damaging?
Per this Maxim app note


  SATA/eSATA signals resemble standard LVDS, and are AC-coupled on a pair of 100Ω-balanced transmission lines. Signal levels are nominally ±500mVP-P.


PCIe has a swing of 175 to 1200 mV (PCI Express System Architecture). So you should be able to do what you want to. But I wouldn't recommend to try this; high speed routing requires care.