You should be able to suppress the warning by adding Import-Template: *;version="0". This is telling Bundlor that you've made a conscious decision that you're happy for all of your imports to match any export version. If you have specific versions for which you'd like to be more restrictive you can still specify those in the Import-Template header - Bundle will only fall back to the * entry if there isn't a better match.
If you know that there's only a single version of a package in your system, or that your code is compatible with all of the versions that will be available then I don't think there's anything wrong with having a zero to infinity version on an import. It may cause problems where there are multiple incompatible versions of a package available but these can easily be fixed as they are encountered by adding an entry to the import template.