Girl Genius XXV: It needs work! BUT THE CONCEPT IS SOUND!

[Spamotron]

Except Othar's plan won't work. As Rodin notes:

Entire towns can just vanish off the map when some local spark has a breakthrough and their monster burns the village down (or on a grander scale, see Passholdt).

There's precedent of Sparks just appearing in places with no history of Sparks before. Until the origin of the Spark and how its inherited is understood killing all the current Sparks is just a temporary stopgap.

You could make the assumption that all Sparks have a Spark ancestor in their family tree and exterminate everyone related to a Spark (Which is a lot of people. For example the former Master of Paris and his vast extended family only some of whom are sparks. Or Ghengis Ht'rok-din founder of the Heterodyne family is clearly at least partially a Ghengis Khan expy. Imagine how many descendants he has that don't know it.) and it still might not even work because we don't know where the first Sparks came from at the start.