I thought it was uncharacteristic for the 1st seat to accept Soma as his aid, but it makes sense from the perspective that he would only use Soma to benefit himself. This also confirms once more my analysis from a while back that Azami's system solely is meant to use everyone like whetting stones to sharpen the Elite 10. Yes they would pick up something along the way, but in the end they would be nothing more than lower, half-assed versions of the Elite 10.
And I sincerely doubt that this actually will lead to a shokugeki. Soma really can't take on yet the 1st Seat and win, but at the same time he's really not going to join central. Erina and Hisako will probably storm in and drag him out screaming he's not going to pull impulsive crap like this a 2nd time. Nice though that Eishi considers Soma's worth enough to put his seat on the line.