What is the disadvantages of the Employer stating the activities on the activity schedule?
It is not really a case of what disadvantages are there in the Employer stating activities on the activity schedule, but more a case of why would they want or need to do it? Under option A the activity schedule is a payment mechanism for the Contractor, so why should the Employer want or need to dictate/shape how the Contractor should get paid when it is the Contractors price and programme to manage?
The only real reason an Employer (under NEC3, Client under NEC4) should want to give an outline activity schedule at tender stage is to get a consistent comparison back from all tenderer’s at tender stage. However, I would call this a “tender comparison” document and make it clear that Contractor’s should feel free to break it into more detail and add more items to it as they see fit,. I would then submit the high level one, but also submit a more detailed one and reference that one in Contract Data 2.
Under option A the risk in the activity schedule is with the Contractor. If the Employer produces it - it could muddy the waters as to whose liability that is (although contractually it is still very clearly the Contractor’s).
So other than a tender comparison document from different submissions, there is no benefit or necessity for the Employer to produce a Contractor’s activity schedule and at tender stage they should call it something different anyway to avoid that confusion.