Yes, all good ideas. Now just need the time to try some of them
GWD, your diagram does not match up to my tractor, here is a picture of the other intact side. Also not sure if I can drill through the case because I don't know if it is hollow and contains vital components.
The first picture shows the bolt that comes out to allow the pin to come out. The second picture shows the outside of the case, where the pin is captured.
Skip
Ah, thanks for the photo. So the tab that broke off was attached to the shaft. Then it appears the bolt holds the shaft/tab in position. It does not seem that the shaft would be threaded in that circumstance since rotating the tab would be required to remove the shaft. Had that been the case then there would be a bolt head on the shaft instead of a tab. Such a bolt head could be secured in a number of ways. So the shaft should just slide out.
Of course, a new replacement shaft/tab would answer that issue quite nicely. So would taking off the existing shaft from the intact side.
It seems like you just need something to be able to grab onto the broken end and then slide the shaft out. So perhaps drilling and threading a hole in the broken end of the shaft would allow an inserted bolt to be grabbed. Unfortunately, the shaft is likely hardened metal so welding on a bolt may accomplish the same thing with less of a problem.
Welding on a washer/nut works very well for threaded shafts but not so much for sliding shafts. A short bolt would allow some leverage (or a slide hammer as previously suggested) to grab onto. However, the access to the area looks a bit limited for larger tools.
As far as the solid outside pin containing structure is concerned, and despite comments from the uniformed, there is no way that structure is hollow and contains hydraulic fluid. Drilling a small hole in it so the pin might be driven out is logical.
Kubota making that structure hollow, full of fluid, part of the hydraulic reservoir, and also having a blind hole for the pin cast in one side is completely illogical and contrary to engineering practices and principles. That tab would be so weak that snapping it off would be a common occurrence given the stresses on the lower lift arm. But consider the source.