A few questions as I try to wrap my head around what can and can't be done with the Droid Tech Specialization and the Droid templates.

Is it possible to program multiple Directives?

Is it possible to upgrade a chassis to Rival?

Is it possible to improve Skills (or even add Skills) after the Chassis is built?

I don't have a problem with the Advanced Combat Chassis or the Elimination Directives being so difficult to complete, but if I'm reading things correctly it seems like buying a standard droid will give you something far more capable for almost any other situation.

One directive.

Not sure what you mean upgrade, you can just choose to make a Rival chassis.

After the programming I suppose a GM could houserule spending xp or something to add Skill ranks, but adding them is done in the initial roll.

I'm not going through all the charts but if you have a well built experienced PC you can make some pretty unique crazy droids.