Monetary incentive will naturally, over time, put monetary incentive as a driver, if not the primary driver, of protocol development decisions.
I have an idea for an alternative, that does not change the game theory of incentive to run a node being tied with the benefit of the protocol/network itself.
There are a lot more non-participation nodes than there are participation nodes, because fundamentally people need a reliable node to transact with. The motive is inherently there for a robust reliable fleet of nodes across the network. Removing the ability for non-participating nodes to transact will provide the missing incentive for participation in consensus. Furthermore, higher transaction rates should require higher stake.
Thoughts?
Edit: Clarification.
What I mean here is that all nodes would have to be participating nodes. So that any node broadcasting transactions is also participating in consensus. From there it could be considered whether to put limits on txn broadcast volume based on the stake of a given node.