Fully offsite scheme of work implies that all project activities (including business analysis, requirements collection, production, etc.) are performed remotely. Both parties stay at their locations and communicate by phone, emails, video conferencing, instant messengers, etc.
Taking into account all the advantages and the disadvantages, we recommend the fully offsite scheme of work for small and medium-sized projects, with clear requirements and with the projects that do not require deep analysis.

Advantages:
Ability to thoroughly analyze the client's organization and gather business requirements.
Face-to-face no limit communication.

Disadvantages:
Travel and accommodation costs.
The scheme can be suitable for projects where the requirements are not clear or client analysis is required.

We recommend partly onsite activities for large projects. It can be reasonable and effective to shift between the above two schemes when required.