This is something Dash does (with the condition that 1000 Dash be held by the node operator to be eligible for a portion of the block reward) so I'm curious if it would be practical for ZCash.
There are no "nodes" in zcash because it uses a completely different setup to create decentralized transaction privacy. You may want to review the original paper describing the goals and approach, it can be found here: http://zerocash-project.org/paper
Oops... How did I miss that? Thank you for pointing it out - that's quite a deviation from the bitcoin model and a rather definitive way of addressing the issue of unrewarded effort.