To install and run an LN node, you would also need to install bitcoind, unless you're using something like Neutrino. But if you are already maintaining a 24/7 full node, then you can install and run a Lightning node with it and charge for routing fees.
I get the point, but IMO it sounds like incentive to keep existing node running rather than incentive to run full nodes.
Additionally, unless your LN node have routing path/directly connected to lots of other LN nodes, i doubt you'd get sufficient income/reward.
It was more like a shower thought idea, than a definite solution to incentivize existing/running nodes. Maintaining a full node 24/7/365 has costs, especially on bandwidth. At least there's an idea of incentivizing them, than none, if the Lightning Network scales.