there is no point to doing anything to the tube other possibly tig welding it. I have thought about putting two gussets from the seat stays to the top tube in situations like this. Alternatively, You could add a sleeve around the top tube. I have no experience with either repair. The fundamental problem with this frame is that they didn't reinforce the seat tube. There are actually a lot of stresses passed through from the seat stays to the top tube, and that will crack something, usually the seat tube. That's why bikes that are built to last either have a sleeve there or an externally butted seat tube.