given that UAs are found in a shell 135-150LY around Merope, that would imply they were launch from everywhere outside of that range.
It makes much more sense that they either came from Merope, or that they came from some other, unknown (omg it works on so many levels!), place and they somehow dropped into these systems and stayed there to mark Merope in some way.
I've long been a proponent of the idea that they came from Merope. Which could of course be wrong - they might simply have been stationed there.
But I don't think they're heading there, though - because I think they'd have got there if they're able to spread themselves across 3,800,00LY3 of space.
Does make me think, though...
Where was that first free floater found again?