Is there a downside to creating the template?
One issue would be in GEDCOM exports. It is much easier to understand that a link generated by the "{{FamilySearch Image}}" template links to an image on FamilySearch.
But what would an "{{ARK}}" template link to? N2T.net... N2T is just a resolver, not the original publisher.
Then there would also be an issue in crossover templates. Using the FamilySearch example from earlier, members could then use:
{{FamilySearch Image|77JV-NZ4X|2}}
or
{{ARK|61903/3:2:77JV-NZ4X}}