Allow extra time compared with a straightforward single-employer case, since the structural review itself takes real work before any filing timeline starts. The employer's willingness to restructure the arrangement, if needed, also affects how quickly this moves.
Expect the structural question to set the pace
Do not anchor a start date to the design work's own deadlines until the employment and profession questions are settled. If restructuring the working relationship is necessary to support TN, that conversation with the employer takes its own time and may not align with the deliverables already scheduled. Build in a checkpoint before assuming any date is workable.
Work backwards from the first date the applicant must lawfully be doing the work, then insert the steps that have to precede it: the structural review, any restructuring the employer agrees to, the credential evidence, and the employer letter. Only after those does the admission or petition step belong on the plan. A Canadian citizen may generally request TN admission at a port of entry, which is quick when the file is complete and immediate in the other direction when it is not; an employer petition on Form I-129 is an alternative with its own processing time.
Neither path shortens the preparation. Build a checkpoint at which the plan is reviewed against what the employer has actually produced rather than promised.