It's the same character just in a younger body.The Goku most people want isn't even the main character of GT for the majority of the time. Hence why this topic was created in the first place. Goku in a kid's body is not the same as him in an adult body (unless you want to be technical about it).
Secondly, why does Goku have to remain the main character? DBZ ended with Goku flying off to train this stranger. The Kanzenban ending throws some symbolism in there that indicates the start of a new generation.
GT is an entirely new series, not DBZ, so they could have successfully (or not) gone that route. Regardless, the path they chose was a flop among fans. As for a tech person, that's why I chose Bra. Like I said, the characters would have to be re-written for it to work the way I see it cause their portrayals in GT are absolutely horrendous.
GT is still DB, albeit without the original author, and Goku IS Dragon Ball. Goku's most suited for that role because he's the heart and soul of the series. The tone of DB fits Goku's character the best. I honestly think people prefer the idea of the next generation than they would its actual execution. I don't recall ever seeing a series that was as good or better after changing main characters.
You chose Bra, but we don't really know anything about her. At least Trunks there's a familiarity with him and an emotional connection. The stories can just build on that.