Somewhat agree. Battling ropes might be a good way to go for upper body dominant rope based conditioning (never tried them myself).
Rope climbs? Less so. In a sense, I climb rope for a living (tree work). It can be a great workout, but it's really all legs and abs with some grip elements. A person without at least decent technique will fatigue long before they get a decent conditioning effect, in my experience at least.
OP, I think you're on track with the sledge hammer and tire thing. Great bang for your buck. Go to a tire shop and pick up an old tire for free, grab a sledge and you're good to go.