Posted: 26/06/2016 at 16:52
Get rid of it, it will never be a shapely tree once it's as you describe. They're not particularly shapely in maturity anyway due to the thick trunk of the rootstock plant being out of proportion with the delicate branches of the grafted part.
A climber through a dead/dying tree look just like a climber through a dead tree for a few years til the tree rots and falls over.
A pergola for the rose would be a better course