The other option is to add vertical support tubes to each side of the gate, then remove the center cross rail and cap the newly exposed ends. In either case it is much easier if the welder can tack the new pieces in place prior to removing the rails for the final welding/polishing
Ken speaks the truth. He witnessed this modification recently first hand...on my stern. My stbd stanchion base was cracked as well, so it was a prime opportunity to make the mod. A variation of what Phil said, connect the wire to a fish tape or coat hanger after you cut it (I had plenty of slack wire in the lazarette behind the engine panel) , push it a fair piece up the rail away from the welding. Pull it back down when you're done.
I'm tickled with the modification. The swim ladder now folds properly into the pushpit. MK1 owners know that horizontal rail is a PITA when accessing the swim ladder...I suppose I now have a MK 1.10