Placing the Galactic Barrier at a specific location risks being a fallacy from the get-go. Sure, it looks like a purple ribbon up close. But if it is a purple ribbon, then a ship capable of warp speeds should be able to go "above" or "below" it easily enough, and
a) a mission to probe through it to see if it is a threat to exploration beyond is idiocy, and
b) an outsider trying to enter will only crash into it if an idiot.
If, OTOH, the thing does surround the Milky Way in the form of a shell everybody has to brave on his way in or out, no matter the path, then we can ignore the ribbon shape as an optical illusion - but we also lose any geometrical connection to the arbitrary rim of the galactic disk.
We would do well to say that the purple haze wraps all the galactic arms, defining an "in" (with lots of bright stars) and an "out" (with dimmer even if not fewer stars). The nearest bits could be very close to Earth in that case. And getting through those wouldn't yet take you to intergalactic space, only through the first hurdle. "Is There in Truth No Beauty?" doesn't really affect this, as the ship seems to enter an alien realm rather than any specific spot in space (indeed, this is the very problem calling for Medusan intervention).
One consequence of this is the likelihood of Janeway having to penetrate the Barrier a dozen times on her way home. Perhaps it's only a thing near Earth, around the Sagittarius Arm or whatnot? (Perhaps the identically colored and somewhat similarly behaving Nexus has something to do with it, too?)
Timo Saloniemi