You need a special wrench to remove the cross-shaped nut that holds the drain. You may need to cut the side of the nut with a thin hacksaw blade if it resists removal, but damaging the tub isn't an issue in your case.

Go metal or ceramic if you can -- plastic tubs feel like jello.

Is he sure that he wants a tub? If I were doing a house with 2+ bathrooms, I'd have one "hot tub" with soaking capability and jets. The other bathroom would be a "wet room" with a stepless shower. Any water spilled on the floor or used to wash the floor would simply go down the drain rather than leaking out. Very popular in some countries abroad and makes good sense:

http://www.livinghouse.co.uk/acatalog/shower-sail.jpg