Why not just use Bitcoin Cash? Bitcoin was designed to compete directly with Visa's transaction rate and still can. I don't get why people don't simple use what works?
The only thing stopping you from adding payment channels on top of that is transaction malleability, but I am not really caught up on the topic.
That's arguably past the point where running a small node is viable, so I would argue you're well into the territory of losing some of the decentralisation properties you want in a cryptocurrency
small nodes don't matter. They can prune or shard the blockchain.
What matters is the economics of medium-sized nodes that are operated by small buisnesses. These are are the entities that have material reasons to run a full node (to accept transactions in an automated manner while preventing theft), and these are the entities that evaluate the rules of the cryptocurrency at the time of transaction.