Yeah, Paizo scrapped the "no multiclassing with a parent class" idea for hybrids. I see no reason why it should be restricted for gestalt. At best, you're creating a character on par with other gestalts, who trades their flexibility for focus. at worst, you get something that makes you ask, "why bother?" (Hunter / Druid and Witch / Shaman for instance, seem like terrible combos.) it's far from overpowere, and for the sake of swashbuckler / Rogues everywhere, I say, let them be!
So are we just lobbing out character ideas for any of the ideas, or...?