Back to Garden au
How would the Confrontation between Garp and Dragon look if teenbean Dragon never got his memories back? You wrote that People would Mourn but how bad would it be for Garp?
The temptation for Garp is to try the entire Marine thing again, but he also knows what happened the first time (and also, what happened to Dragon as a teen this time as well).
Plus. Well. What happened with Ace. There is more solid proof than ever that trying to get his kids to become Marines isn't enough to protect them and that is such a devasting blow to Garp's concept of the world.
I'd say that Garp is so much more tempted to sacrifice himself for The Youth than he is in canon (and the man is already attempting to throw himself on metaphorical mines ALL THE TIME for this in canon!!!) because Dragon isn't grown up to a stage where he can properly protect himself like he did as Revolutionary Leader and grown adult, in Garp's mind. He has to protect his son.
Also, I think Garp would want to introduce Koby and Helmeppo to Teen Dragon. :)