The issue with Richardson is this makes it only an American game - of which he has made an impressive contribution but no one individual is capable of handling it all ...and the concept of a gateway ancestor is something to which the rest of the world is oblivious.
For example, the Anglo-Irish are teeming with ancestral links to Magna Carta, and a few of them are still there today.
To walk beyond Magna Carta specifically, to the general concept - how would we ever address such a label.
Classically, in Americana - they are people that crossed the pond generations ago and a long time ago.
So how would I and many of my peers look at Euristo?
In my particular case, my fourth great grandfather, the last baron in our family is in the Baltic Noble register...and I have at their satisfaction completed out the rest of his entire career to his grave - and a growing extensive biography for the historians among them.
We don't clamor to join Aristocratic societies - because in our world you are noble or aren't - and we aren't American
But if you were to posit a gateway ancestor who would it be?
His daughter apparently the only one with children was born in England, her mother - his first Baronin (but translated back to Baroness in English) born in St. Kitts also with such ancestry.
His grandson, my second great grandfather and the only surviving male line was born in Northern Ireland. His father also has proven Magna Carta as well does his wife in the Hunt side.
Referencing back to Ireland, there are several other lines with very solidly proven or most like scenario (like all others are unlikely) Magna Carta ancestry
His oldest son was born in Cashel, his oldest son was born in Dalkey, his oldest son was born in Vom Nigeria (his mother has proven descent from Richard More) and his son me, born in Montreal, Quebec, his son born in British Columbia, his son born Nova Scotia.
So please tell me who is the gateway ancestor there?