I'm not sure that intent should be at all relevant. If you're not capable of routinely keeping the vehicle within the speed limits, then perhaps you shouldn't be driving it?

If you're caught once, then a fine and a slap on the wrist should be enough to make you pay more attention. Twice - bigger fine & harder slap. If you're caught N times, then lose your license.

Something like "ignorance is not an excuse in the eyes of the law".