We have a standard application form online that covers key information that we need to know - things like driving licence, nationality and work visa status - as they can impact on the role. People can then either fill in a form for the remaining details, or upload a CV,
Many firms use standard forms as a way of simplifying the administration of the application process, and to create a level playing field.
I would never ignore a form provided, of for that matter any application instructions relating to the CV/resume length, detail and/or cover letter.
In our case, if the online submission is not managed properly, you are rejected automatically by the system. I can scan reject applications, but realistically its unlikely unless I'm unabel to create a shortlist from the applicants I have.
In some industries, especially the creative ones like advertising, a CV that simulated an application form (good or bad) could create a stand-out point of difference between your application and others. It would need to be undertaken with significant style and flair, however, or it could easily misfire.