New Application Server

Here in my company we use an unique AS400 as enterprise server and we intend to buy a new one. Since the old one does not suport an upgrade, we´d like to use it as an aplication server. Does anyone can give me some hints?
Is it possible to use an AS400 as aplication server only? How is the dificult during the future OneWorld upgrades?
Thank You.

This is definitely possible. Just follow the install steps in the AS400 install guide. Future upgrades and service packs won't be an issue.