Poor mans one pipe system

I got a call to check the radiator heat in an old house down in DC. I had installed a kitchen radiant floor 7 years ago and the lady who was the home owner loved it a lot. However in the rest of the house she was having heating problems. Some of the cast iron radiators were not heating up properly. Someone besides me had piped the radiators, but right after they were done, she had  she left town for 6 years to live in France. (sweet!) She rented out her house in that time period and had never noticed the problem with the radiators. This is her first Winter back and she noticed it just wasnt right. As I stumbled around the clutter filled basement It was hard to figure out the piping. A lot of it was covered up with air conditioning ducts installed after the radiator piping and the piping was covered up. When I could see it it didn't make sense. It was copper piping leaving the boiler at 1 inch id copper. Down the run I could see 3/4 inch branches reducing down to 1/2 inch copper and then after a couple of tees to a nearby radiator it would enlarge to 3/4 in copper again. It eventually dawned on me that someone had installed a one pipe system, and instead of using mono-flo tees they had reducing couplings making the resistance that a mono flo normally would. It was kinda clever but it didnt work very well. The big old cast iron radiators, originally from a gravity boiler system, gobbled up the heat really fast and by the end of the run the water was no longer hot enough. There was no good way to balance the system between the different sized radiators. Some where small and some humongous. What a nightmare. I might recommend replacing it all with a radiant floor manifold with pex runs to each radiator, so there can be hot water to each radiator supply, and some balancing could be done if need be. Just when you think you've seen it all you see something new.