But you could try to do it on a virtual server.
In another hand, you could have some problems when you'll make an Elastix update.
I think at Freepbx rpm, Asterisk rpm...Etc
And I don't talk about some dependencies like Dahdi, Libpri.
look with google translate my articles "deselastixando elastix parte 1 y 2" en s i n o l o g i c (deelastixing elastix parts 1 and 2)
there i post how to upgrade kernels compile manually asterisk 1.8 dahdi etc...and how to use tls sip encryption and srtp voice encryption