This might look similar to post Add more pre-defined item types, but:
It would be very nice, if i could build my own templates (predefined item types) myself. so everyone is capable of putting those fields into his templates he needs. You will never find templates that fits for everyone in every country. So it might be the best way to let the user do this work.
This might be a lot of work for the programmers, but today I have to put my custom fields again and again into every entry (since there is no copy/paste oder duplicate feature for those actions).