I don't believe that most people will be upset with following directions from the legal team, especially since maintaining some consistency between language editions helps editors who are not native English speakers.
I like your "appeal from the developers" idea.  In my check of recent watchlist notices, all but one used passive voice, but I think that your marketing sense is better than the previous posters there. 
Formal testing on naïve users is already being done; you can see a brief report on the latest round at mw:VisualEditor/Design/User testing.  In addition, VisualEditor is being used, with apparent success, by thousands of IPs and newly registered users each day at other Wikipedias.