The burden mechanic works really well as a risk/reward control. Accrue too much ore and you'll have a hard time getting back. Adding in some extra penalty for dying along the way would probable accentuate this tradeoff further. Otherwise, the ore and upgrade economy felt pretty well balanced. I would recommend changing the default ore behavior to be "keep" rather than "discard" since I usually just wanted to keep everything while mining out a line of rocks.