mmm......having to move a lot of pipes? Water/sewage etc. Changes to the foundations? Possibility of flooding?
As to the first Q, we don't have a culture of basements except in Georgian/Victorian houses - often dark, damp, and dank.
You need to make sure that who ever is doing this knows what they are doing & have experience in this area otherwise you'll be looking at a pool of water in the basement in time to come.
You may need to incorporate this into your planning also - not 100% about that though