We would really prefer you avoid that if possible, since the setting is purposefully ambiguous, and we haven't made mention to any of the older regions at all for a reason. Without telling you our plans, it would be difficult to tell you how to approach the idea of a 'Johto heritage'; for example, it's entirely possible that the game is set in Johto and that this revelation fuels part of the plot later down the line, which would cause troubles for you later on. Hopefully you understand what it is I mean.

Gold is welcome to have a special interest in Johto legendaries, though.