Cutting out the shaft is a tiresome task and will possibly result in damaging the top arm.
I will detail a couple of other options for you.
With the locating plate, the thick thrust washer and both nuts removed, replace the thin retaining plate with a thicker piece and refit the nut. If the shaft is siezed in the bearings it will not rotate. tighten the nut as to act as a puller, drawing the shaft until it buts up on the thick plate. Continue with this increasing the spacer thickness until things start to move freely.
Another option is to rebuild the arm and tighten all the nuts up.
From you picture you have access to the arm, remove the shocker pin release the top ball joint and fit a suitable piece of pipe over the arm. working up and down might promote a bit of movement, just like freeing off a stuck nut.
My last and final option, which may sound drastic to some, but one that has to be employed sometimes is to cut a hole in the vehicle floor giving access to the pin. The pin can be drifted out from inside the car and them a plate fitted and welded up.
Heating the arm around the areas where the bearings are might help in all of the above.
Thats my take on things.