There is so many ways a skater can be nicked and dimed on TES, there should be equal scrutiny to PCS. It is a measurable quantity, so it should not be based on a vague feeling of either the judges or the audience as much as possible.
Competition scores should not be based on feeling of the audience. They're not judging, and most of them are not experts on skating technique.
Historically, Presentation scores under 6.0 were based on holistic impressions of the whole program by trained judges.
Under IJS, the aspects of the whole program are broken down into (now) three separate areas of the whole program, but they're still primarily scored holistically for each component.
Here are the current program component criteria:
Composition
The intentional, developed and / or original arrangement of the repertoire of all types of movements into a meaningful whole according to the principles of proportion, unity, space, pattern and musical structure.
Unity
Connections between and within the elements
Pattern and ice coverage
Multidimensional movements and use of space
Choreography reflecting musical phrase and form
Presentation
The demonstration of engagement, commitment and involvement based on an understanding of the music and composition.
Expressiveness & projection
Variety of contrasts of energy and of movements
Musical sensitivity and timing
Unison, oneness and awareness of space (Pair Skating, Ice Dance, Synchronized Skating)
Skating Skills
The ability of the skater to execute the skating repertoire of steps, turns and skating movements with blade and body control.
Variety of edges, steps, turns, movements and directions
Clarity of edges, steps, turns, movements and body control
Balance and glide
Power and speed
Most of these criteria are qualitative, to be scored on range (of 0 to 10 with 0.25 increments) rather than simple yes/no decisions like most of what the tech panel does. And the different criteria within the same component need to be balanced against each other.
Do you have suggestions for how these could be better quantified into numerical scores, within the time allotted during and immediately after the performance?
Judges need to do as good a job as possible on scoring those components overall before worrying about scoring caps for Serious Errors. First come up with the overall score for that component, and then consider how errors should affect the overall score.
"Serious errors are falls and/or mistakes which result in a break in the delivery of the program. This break can be minimal or more pronounced and noticeable. These errors must be reflected in the mark awarded for each program component. The consequence depends on the severity and impact they have on the fluidity and continuity of the program."
Falls are defined and called by the technical panel to receive fall deductions.
Other kinds of errors/breaks are more subject to interpretation -- different judges (and different fans) might see different levels of severity to various errors. There will probably always be some subjectivity in determining whether a break was "minimal" or "pronounced and noticeable." And even the same kind of error may be more or less disruptive depending on exactly how that skater executed the flawed move at exactly that moment in that particular program, and even depending on the viewing angle. So it's difficult to write rules in advance that certain kinds of errors should always receive exactly the same penalty. That's why many of the negative GOE values are a range of -1 to -2 or -2 to -4, etc. The same would be true of any program component reductions.
Everyone may have their own pet peeves, and their own areas of particular expertise, so there will always be some differences of opinion.