could Lightning decentralisation be improved by giving node operators a "do not route" config option?
Node operators are already able to create private channels which are not announced to the rest of the network.
I don't mean that at all
I mean:
public nodes, with publicly announced channels, NOT routing through specified nodes (e.g. nodes with high amount of channels) to prevent routing from becoming dominated
What if some nodes somehow faked (lowered) the number of their channels? A channel is considered not capable of routing when it is offline. What if it could be exploited in some way?
right, sybil style de-identifying. LNbig already split themselves into multiple nodes, but (obviously) they continue to identify themselves as LNbig run nodes
that's why I also mention positive preferential routing, i.e. a "please use these nodes to route, if possible" routing algorithm
that way, a node operator can choose a bunch of nodes for whom they know (or are at least confident) are run by small independents, and make sure those small independents always get favorable treatment when routing
possibly, large trampoline (routing delegation) nodes could be similarly shown routing preference if they have a "good" preference list, but I don't think it can be proven that trampoline nodes were using routes that avoid hubs, at least with how the Lightning routing protocol works now... not sure about this