I don't know how much I can add to the discussion, as the above responses have been very well thought, but here's my $.02:
The entire goal for the OP is accountability. With a metric of productivity, he will be able to prove who has and who has not been working the way they should.
Here's what I don't understand:
If you have proved the internal conspiracy to pilfer extra money from the company and risk missing deadlines for the customers, and that hasn't gone anywhere, then why would tracking drafting hours offer any more accountability among the team?
An entire department colluding to sabotage projects with unnecessary delays is a problem that should be dealt with first, IMO.