So these battle droids take Han and Luke in for questioning, seeing Luke's lightsaber, they realize he is a Jedi and therefore a soldier for the Republic. There are far too many droids for Luke and Han to take on alone, so they decide to play it safe and wait for an opportunity to escape, return to their ship and report the situation to the New Republic.
As it turns out, the situation is worse than they thought. This remote planet is not only home to a remote garrison of battle droids, but was in fact the site of one of the Seperatists droid factories. These droids are following their last orders they received just before the Clone Wars ended: "Defend the factory as it continues production of more droids, and wait for further orders." The planet contains the natural resources needed for droid production, and beyond the droid factory (or perhaps multiple droid factories) it has mines and all other facilities needed to continue producing droids indefinitely, and has been running non-stop for the last 30 some years. The planet contains millions upon millions of dormant droids (and the carriers to take them off planet) just waiting to be switched on so they can continue to fight the war they have been programed for.
What is more, this droid production facility was placed on this remote, uncharted planet to produce special droids programmed specifically for an assault on Coruscant. If they make their move, then it would take all the forces of the New Republic to stop them, and likely that wouldn't even be enough. Either way, we are looking at a massive death toll. Han and Luke are going to have to find away to shut down production, and keep the dormant droids from becoming active. Maybe even activate some sort of self destruct sequence.
Perhaps among the planet full of droids, there is a lone human engineer running the whole thing. A member of the Separatists back during his day, he was left to oversee production and was waiting to hear from his superiors. When he never received any further orders or news, he realized that the Separatists must have been defeated, and has lived in isolation, just he and his droids all these years, now elderly and somewhat insane, waiting until he felt he has enough droids to exact his revenge and take down the Republic once and for all. The Separatists army would be victorious, even if there are no Separatists left to celebrate it.
There is a bit of plot for you (Almonkey had a cool idea actually), take or leave what you like.