Instead of fining drivers, how about a “sin bin”.

A mandatory session sit out requiring another driver to take their place. Serious offences could be one or more weekends out, minor offences just one or more practice sessions.

This has no bearing on driver earnings, other than future contracts based on penalties. It also gives more chances for reserve and junior drivers to get a drive.

Edit: Now I’m imagining a top gear stig waiting in the wings for a driver error. Maybe the stand-in drivers are picked at random from an FIA approved list rather than the team themselves.