@Richard Talbot are you talking about a complete tear down and rebuild? If so, I put alot of trust in my architects and design team. Additionally, with any development, you have to play by the rules of the city (which can be a good or bad thing). I would say that unless its a massive complex in a metro area, using common sense like attached garages or potentially having an elevator would always be a good addition (assuming that you can recoup those added cost). Now a days I see a lot of smaller developments that go over the top with the amenities because they feel that that is a big driver for tenants and boosting rents. Sometimes that is true and sometimes they just overbuild. Really need to know your prospective client on what they care about and are looking for. I would say letting your experienced architect/designer run lead on that is the best scenario for you.