Are you working on the game? Who are you people to say how much time they have to add something to the game.
I don't need to work on the game to understand the logistics behind changing something. Do you understand game design at all? or even programming? it's not as simple as "lets just add it".
As someone who understands game design and game programming I can give you some reasons or differences for one or the other.
FP needs less animations for the main character than TP but if you have a lot of cut scenes and a ton of NPCs the extra effort decreases more and more.
As there is character customization it doesn't make much difference if you can see the character during game play or not.
You can save a bit performance by not rendering the main character (which has to have lots of detail as the camera is near him).
Camera is one of the biggest points, in FPS you have the total control over what the player sees. You can make the character look at something and the player sees it also. This gives you a lot of possibilities for story telling. In TP the player can easily miss something or if you interrupt gameplay (happens also at forced view in FP) for a short cut scene, the interrupt in TP usually feels harder than in FP. Also a small interrupt in FP can be really short, just a few seconds and the player would not really feel it. A cut scene of a few seconds is still a cut scene.
Also camera movement/control is a bit more complex. in FPS the camera = player, the camera is limited to the player movement. In Tp you have to have character movement and camera movement, you have to take care what happens in small rooms/when the camera collides with walls. Also the camera can see things the character doesn't see, so they also have to be there. In FP you can spare out parts of the environment that can't be seen.
EDIT: Oh and I forgot dialogs, it is less immersion breaking if you just focus the FP camera on a person and just do the dialog than switching to a special dialog view in TP, it is also easier to implement and you don't have to do face animation/lip sync for the main character.