The gospel of the kingdom (which absolutely includes obedience to the law) will be taught by a royal priesthood (of Israel 1 Peter 2:9 KJV) to Gentiles after the second coming (Matthew 29:19-20 KJV), but it won't happen until then (Matthew 10:23 KJV) and that's not the gospel of OUR salvation (1 Corinthians 15:1-4 KJV, Ephesians 1:13-14 KJV)!
The royal priesthood is a spiritual metaphor, which is why we offer "spiritual saccrifices". You know? not literal physical ones?
Besides, lets compare Peter with Paul......
1 Peter 2:9 But you are a chosen generation, a royal priesthood, a holy nation, His own special people, that you may proclaim the praises of Him who called you out of darkness into His marvelous light;
This special people have been called out of darkness and into God's light.
Acts 26:17-18
‘I will deliver you from the Jewish people, as well as from the Gentiles, to whom I now send you, ‘to open their eyes, in order to turn them from darkness to light, and from the power of Satan to God, that they may receive forgiveness of sins and an inheritance among those who are sanctified by faith in Me.’
So there we have it. Gentiles also being called out of darkness to light, to be sanctified spiritual priests.
And as to Gentiles like the syrophoenician woman seeking for her daughter to be healed: she feared God and recognized her place as a dog eating the crumbs under the master's table. In doing so, she placed herself in a position to be blessed (Mark 7:25-27 KJV). The centurion knew to go through the proper channels too; the order being counted "worthy" (Luke 7:4 KJV) of a blessing. And what is it that made him "worthy"? Luke 7:5 For he loveth our nation, and he hath built us a synagogue.
Both were perfectly in line for a blessing as per Genesis 12:1-3 KJV! Again, neither of which have anything to do with Gentiles such as we (Ephesians 2:11-12 KJV) or the gospel of OUR salvation (1 Corinthians 15:1-4 KJV, Ephesians 1:13-14 KJV)!
Let's be really simple here, because it couldn't be simpler, even for a madist. Is faith the subject here?
Ultimately, are these people getting what they want because they're seeking it by faith? yes or no?
You are so not wanting to see it this simply.