I would class only the first scenario — i e “the personal trainer is coming into the building to train residents”— as acceptable. The second is bad, and the third even worse. Tharra’s scheme probably already has a by-law prohibiting obstructing other owners’ access to common property except on a temporary and non-recurrent basis. That should cover the situation, but a specific by-law could always be developed and registered (at a cost, given you would probably want a solicitor to draft it and make it as lawyer-proof as possible).