Its not adviced to apply just the offer letter. A letter with the roles and responsibilities is a must and if the official IRCC format couldnt be followed, an alternative must be arranged and the intention of best effort must be shown to the IRCC officer for him/her to consider the file as complete and assess it accordingly. I am not saying that getting a notorized document on a plain paper is guranteed but at least you are guaranteed not to be refused on the basis of an incomplete application.
Thats all in my opinion
Note: when doing that an LOE must be submited explaining the situation in details and attaching to it as much proof as possible to support the case.
Best of luck
