Well, if they get out that early then they're not trapped in Sector 0, and are free to leave for the surface. Azul and Rosso at least are no doubt bloodthirsty and battle craving, just as we know and... well we don't all love them, but as we know them at least. But of course, we still have no way of knowing what the hell they'd be doing without Hojo to direct them into the whole Omega fiasco of DoC.
No matter what they choose to do, whether its just to seek joy in bloodshed or to conquer the world, or what, I know Shinra would react in horror. This is, after all, one of their darkest, dirtiest secrets coming to life. Its not information they want out, even among their own amoral ranks, not to mention the extreme threat they pose to Shinra and the masses of subjects customers worldwide. Plus, DG would emerge right at Shinra HQ, that doesn't bode well for a calm, quiet response from Shinra. I picture every Shinra exec, whether they know who DG are or not, hitting their personal panic button the moment they emerge from below the Shinra Building.
We mention how President Shinra would sic DG on Sephiroth if he continued his madness fueled massacres beyond Nibelheim, or how they'd send them along with the rest of their forces into the Crater if plans to defeat Sephiroth had gone forward in the OG. Now we see the reverse, as Shinra sends every grunt, air unit, roboguard, monster, Turk, and SOLDIER at their disposal in to kill DG, kill them quick before they endanger the board of executives or allow harmful secrets to get out. In other words NO ONE goes to Nibelheim. Everyone from as low down as those goofy guys from Junon who copied Cloud's victory pose in the OG all the way up to Sephiroth himself and everything in between gets redirected with the goal of wiping out DG.
And as I see it, this conflict would be absolutely EPIC.