This is one of the points where the GM needs to sit down with players and hash out how things are going to work. All the players need to be on the same page when it comes to creating characters, and its up to the GM to figure out how to do that. Either by stating outright that you need to spend points on a `Mech, or by letting all the players know that they'll be assigned a `Mech, and thus won't need to spend the points, to keep the playing field even.
Of course, if you do spend the points, you might get what you want when it comes to the Vehicle, while the person who relies on being assigned a vehicle might get what's leftover.
The traits that don't really translate well from Character generation to play (Vehicle, Equipped, Wealth to a lesser extent, Custom Vehicle, etc), really require the GM to take a look at what's happened during character generation and try not to make the person that spent the points on those traits feel like an idiot.
For example, if you spent points on Custom Vehicle just to change up the layout of your `Mech, and then in the first session suddenly everyone wants to have the unit techs modify all their designs, you're probably going to feel a bit miffed if the GM lets it happen without much thought.