In single player JA, you're out of luck, sorry. Yes you can mess with the camera options but it's not perfect (there's a mod on jk3files.com that does this for you, as I said, it just uses scripting so it's not perfect, like I think the camera goofs up when you run backwards with force speed for example).
However in MP, it's pretty easy, just do cg_fpls 1 in console. Then when you switch to lightsaber it will be first person (only).
A better solution for MP is OJP Basic mod, which lets you use both 1st and 3rd for saber, you can see the rest of your body (including your feet looking down, or you can just toggle it so it's just a floating blade) and synchs it to the model you're using (well, most models anyway).
http://ojp.jediknight.net/)