Job title -> pay range. If you do work that does not match your job title (or job description) and your boss refuses to acknowledge it, I'm confident there's existing legal pathways to deal with it - with the help of unions if need be.
I also work in a flat company. Actually some weeks ago, one of my colleagues was applying to a new credit card. So the bank called our HR team to very a colleague's salary. I ended up taking the call due to a mishap on the phone system. So they needed to double check her salary, because she had mentioned 50% raise but no change in her job title. So I had to explain that's the way our company is.
Same problem here... small company, everybody does everything, same title, but different hours and output. I guess we'll have to think of unique position names for everybody
Pretty sure the wording is intentially fuzzy, so the special interest groups can add the meaning after it becomes law.
I would expect them to push for a Marxist view on "value" of work, basically each hour is of equal value, but where you adjust for number of years of formal education, again where the type of eduction is not important. A developer with a MSc from a top college may be compared to someone with an MSc/MA in Sociology, working in the HR department, for instance.
The key alternative is to gauge value based on market demand, but where I live (Northern Europe), those who advocate "equal pay for work of equal value" don't seem to go for that. Instead, they claim that nurses and engineers should have the same salary, as the length of their education is different, at least for people employed by the public.
Even worse is, that a high producing coder with just a high school degree can easily outearn someone with a PhD in ancient greek language by a huge factor. Considering that people who studied ancient greek are most probably receptionists in such company, this will cause a lot of problems in the long run.
Maybe full transparency would solve all those problems (eg. all paychecks are public), but i know people who prefer their paychecks private, because of otherwise modest lifestyle, their landlords would increase their rent, and random family members would come begging for money.
That seems doubtful. Europe might not have as much of a hard-on for free markets as the US does, but they aren't, by any stretch of the imagination, on the verge of abandoning market economics for labor.