I suppose it depends on the setup. I doubt very much that making FS models would ever pay the rent as a fulltime job.. more something to take up ALL of your time not at the 'real' job as a supplimentary income. Some firms work it that the model maker takes a percentage.. others, you are on the payroll and get a salary. Ideally, the organisation you 'Produce' for should supply as much info for the project as is possible but I doubt that is ever enough. As a one man show.. you have complete control but no support.
I doubt if there's an ideal solution really as each producers situation is different as are each employers rules of engagement
Wouldn't be for me but I'm no good anyway having neither the time nor talent
To my knowlege, Dan Dunn from AS is the only full time FS developer who is an employee in the world, but I stand to be corrected. Pretty much everyone else owns thier development company or works as a freelance on a pecentage of sales basis.
I have yet to see a full FSX (SP2) beta myself,but I have seen some screenshots . Hopefully the old 95% complete FS9 model might see the light of day as freeware one day.