More blocksize essentially means more opportunity to capture transaction fees. This necessarily leads to an incentive to create bigger and bigger blocks therefore considerably increasing the cost of running a full node.
Yes but...
1. non mining nodes are already doing this altruistically.
Not necessarily. Payment processors have an interest to run a full node to more efficiently broadcast their transactions to the network.
You'd be surprised by the amount of wallet services provider that don't actually run a full node.
Also, I have no interest in a network where only payment processors run nodes.