Thanks you for the answer @TomM2 , appreciate it! 
I understand the difficulty in providing an complete solution based on my loose description.
Well, your tips will do well in our solution, but the most tricky part here is not mentioned. Perhaps i missed out on mentioning it in my first post, but here it goes (another loose description 
)
After the deal is set with the accompaning line-items, we wish that the assigned consultant can either report the worked hours or through an integration with “Float” (Our resource planning software). That way we have a ready to report invoice with the correct data.
Do you have any thoughts about that?