I'm a developer in large IT company that is centered around providing services to clients (by that I mean development department is <20 people and not a major part of organisation). I'm solving different tasks relevant to current problems, and everything is fine so far, but management somehow came up with idea to implement some application that replicates most of features in industry award-winning products like MS's Visio or Autodesk's AutoCad.
They want to do that using available resources I've described above. My first answer was "that's impossible even in your most bold fantasies" because project of such measure is made by dozens of teams of developers/architects/testers, costs millions of dollars and develop-from-scratch period is at least 1,5-2 years.
They consider that, but have few counterarguments such as we don't have any deadlines on this project (legislation behind subject area is not yet done and may not be adopted in next few years) nor detailed specification so each implemented functionality can be considered as minor release that will be delivered to client and tested "on the field". And of course, we don't need 1:1 copy of Autocad, just "few major features like 10% of whole product functionality".
That arguments doesn't help in estimation at all, on the contrary it means we'll have a lot of uncertain requirement changes like "look at this feature of AutoCad and implement it" and test by customers and not professional QA department is (politically correct synonym for idiocy).
Any ideas how to reason and estimate such task? Though some numbers would be helpful, but all development costs/details of large projects are unavailable, I can operate only with such ambiguous facts as average known salary say of Microsoft SDE and timeline of MS Office releases i.e. talking about Visio.