Hi,
This totally depends on the complexity of the project, not only the size. However, you would definitely need more modelers than engineers. I would suggest 2 modelers for 1 engineer. The development is what consumes most time. However, in high rise structure, you will need not less than 3 modelers per engineer. This is so far what we've been doing, but I think that as the technicians get better, the numbers change.
Other input from other users is highly important and valuable as this is a hot debate in lots of (CAD to BIM) transition companies.
Regards,
Ali Al-Hammoud
Structural Design Engineer
MZ & Partners Engineering Consultancy