There is a whole long thread somewhere on here with details of which docks work and which do not. Worth a read.
Another thing to consider is MTTR. I.e. if the laptop breaks, how long will it take to repair it. If it takes 2 weeks for you to receive the replacement part from FW, what is your employee going to do in the mean time? You might want to retain some extra spare FW laptops to cover that eventuality so you have local spares to do repairs quicker. So if user has a broken laptop, you can swap it out and diagnose and repair the broken one in slower time.