Hi,
As you must have seen the nationality form, it does not ask you much of docs as was the case in ILR.
If you read it carefully the form says you have to prove your stay for 5 years in UK and they want you to provide either of two proves for that, the first one is your passport which shows your date of entry and all the visits you made out of country and if you don't have passport then you have to show them letters or other stuff they listed in the form.
I only sent my passport with the application form and got nationality in 4 weeks last week. if you read the form again, home office have not demanded any thing other than your passport.
Take care
Seenan