Hi again, again!
Not sure if I understand your question, but here are some thoughts.
I think that your question is looking at gateway from a different perspective than the Magna Carta Project... from the barons to a person, rather than from a person to _a_ baron. The Project's focus for a Gateway is on the immigrant - the gate being where the "Gateway Ancestor" landed... that person opening the gate/door for all the Americans who are descended from a surety baron.
The Project's focus for those immigrant Gateway Ancestors is to have a badged trail to a surety baron - "a" as in one. What you're asking about would require the identified person to have badged trails to all 15 - if 15, then the two Dads are there too. I say badged trails because trails badged by the Project have been reviewed by the Project and found to be valid. The likelihood that all of the trails returned by the Relationship Finder or Chase's app are valid are slim to none.
So we'd need to find the ancestor(s) of the Project's Gateways who had badged trails to all 15 barons. I don't know of a way to easily do that. Tediously, you could go to Gateway Ancestors category & run up the trail/s of each badged Gateway, checking the categories for each badged profile until you found one with 17 Descendant categories - see the Glossary for the Project's definition of a badged trail and the Surety Baron Index for links to the Descendant categories. NOTE please that the Descendant categories are maintained by the Project and should include ONLY those profiles that are in a badged trail to that baron. The profile you're asking about, Christopher Hildyard is not in any badged trail, but his mother is, to 6 barons... see her categories.
All that said, what you are asking could possibly be the basis for identifying "non-immigrant" Gateways. As I said in my other answer, the question has come up before but not been pursued - mostly because setting criteria presented too much of a headache. But if we only included the "last badged" descendant of all 17 barons, that might work.
For example, Christopher would not be eligible, but once the profile for his mother was connected to all 17 barons, she would be. Or maybe we could lighten the criteria a bit and say 6 or more (or 6 or more excepting those descended from Albini-39 or Lanvallei-3 - they're the two who seem least connected; if you connect to the others, you'll probably connect to most of them). Maybe add a time constraint? Living between 1415 and 1515?
I mentioned in the LiveCast one of the Project's co-leaders, Michael Cayley, who did not have a Gateway Ancestor since Michael's still in England, but looking at his ancestry, you find lots of trails to surety barons. Crawling around his tree, I find the badged profile of Robert Wingfield (who is in three badged trails).
With the criteria of a badged profile for someone living between 1415 and 1515 who is in badged trails to 6 or more barons, includes both Christopher Hildyard's mother and Robert Wingfield's ancestor Margery (Despenser) Wentworth. Then living descendants of these "Never Left" Gateways could use a tailored Descendant sticker to point to them - see the Project's tailored stickers [here].
With criteria as stated (badged to 6 or more, except the 2 barons mentioned & living between 1415 and 1515), I could set up and monitor a "Category: English Gateway Ancestors to Surety Barons". The Project would not actively pursue populating the Category, but would monitor it to ensure only profiles meeting the criteria are included. So... not an official "Never left Gateway" subproject, but would it meet what you're looking to establish?