Do you have exactly one tick mark per data point? If not, then editing the tick marks themselves might not be the best solution as tick marks can change frequency as the user zooms. Maybe you could add an annotation over the missing point or on the axis (perhaps a red exmalation mark or a cross)?
We have logged the interest for discontinuous series as our development is very customer driven. I can assure you that your interest really shapes our development choices. This feature is definitely on our radar, but I can't say anything more concrete at this moment in time.