Just wanted to revisit this, as it is an interested idea. @Witherby any updates?
Thanks for asking. I almost forgot that I had planned this. For one reason or another I ended up not being able to brew this beer until June (three months later) and at that point I just needed to brew the beer and not fool around with an experiment. So I decided to just aim for something like my version of the Bru'n Water Jever profile:
Calcium 35, Magnesium 1, Sodium 24, Sulfate 78, Chloride 34
I am able to reach this with my tap water with some gypsum.
The beer turned out great. I suppose I should try brewing a southern German pils with lower sulfate levels (i.e., even less gypsum) or actually try my experiment, but I have even less time now than I did last summer, so probably not this year.
For now I did see canned Jever at my local liquor store last week, which we hadn't had available before, so I will pick up a 4-pack and hope for inspiration.