Well, what if government changes? There's a chance that SASF would become target number one, because of their sympathies with previous government. I mean, just think of the future consequences. What if it would be Blood Dragons who would prevail in the Kusari?
It's not that stupid scenario, because Blood Dragons could be covertly backed by The Order or even by GMG. Not to mention about possible amnesty from either Liberty or Bretonia, because unlike Xenos, they aren't just common terrorists.
And in case of Kusari joining the Gallic Alliance, enemy of my enemy is my friend.