An interesting idea, not to let upper case and lower case share the same baseline. Just let them hang from the same "clothesline", so to speak, and you get:
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This looks promising, although there are still some quirks. For instance *is* is a good idea to let some upper case characters peek above the x-height? Or should the whole uppercase set dive even lower, like the S in the original lettering on the entrance in Zuidlaren? I have to bear in mind that people will actually use this font so the deviations from the norm cannot be too big. I'll do some puzzling over the weekend.
Update #1:
First result of the puzzling. This image is stored as a GIF-file, so there aro no JPG artifacts that could spoil the image (like the one above):
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Update #2:
I did not quite like the letter Q, so I changed the design. Borrowing some elements from the R gives a much more pleasing image. Judge for yourself:
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Update #3:
This follows a suggestion made by Bill, to omit the 'serif' on top of the E and F. You may also call it a flagstaff, and the initial idea was to create more height in the upper case.