Upgrades in New Construction

Does anyone have any experiences with upgrades done on new construction? I'm not referring to upgrade packages offered by the developer. More like customizations including additional showerheads changing sink basin or upgrading models by the same manufacturer? Are developers open to doing anything different from the offering plan if you play for parts, labor, etc? I figured since there are no walls up yet, it would be a lot easier to do some of these things. And since they aren't neccessary changes, I wouldn't bother breaking walls, tiles, etc on something brand new.