You can reset the footnote counter using
:!footnote-number:
at any time start counting with 1 again. Although the rendered result will look like you would intend it to look, the the navigation between the footnote in the text and the footnote will not work as you would expect.
A quick test of mine revealed that the number is used for linking between the footnotes and the text, so that if you have two footnotes numbered with "1" the linking back-and-forth will not work as expected.
Please give it a try and consider raising an issue on GitHub for the Asciidoctor project.
Will you be using PDF as an output format?