The idea of people just outside of the Elite 10 shouldn't really apply. The training on the train was the way to get them to cook at that level, putting them past all second years. Isshiki is probably the only one at the level of Erina/Souma, but his personality is to not do anything combative. Sure, the other protagonist could lose, but we need a legitimate challenge for Erina and Souma. I agree with the Souma parts, but even that rivalry is friendly. Especially now that she's fallen for him. Either way, we can be safe trusting the plan the authors have. All of the major plot points have been solid and nothing indicates things will change anytime soon.