class Grape::API

def mount_instance(opts = {})

too much, you may actually want to provide a new API rather than remount it.
depending on where the endpoint is mounted. Use with care, if you find yourself using configuration
For instance, a description could be done using: `desc configuration[:description]` if it may vary
The remountable class can have a configuration hash to provide some dynamic class-level variables. 
def mount_instance(opts = {})
  instance = Class.new(@base_parent)
  instance.configuration = Grape::Util::EndpointConfiguration.new(opts[:configuration] || {})
  instance.base = self
  replay_setup_on(instance)
  instance
end