Running X without root

I have a kiosk-style host running Ubuntu Server 14.04. I'm trying to set it up to play some videos, TV-like. Sometimes it needs to play Youtube playlists and other web-based video streaming services etc., so a browser window seems to be necessary.

For this purpose I installed a barebones X.org without a desktop environment and it works.

However, because the administration is over network and the host doubles as a a file and web server (this is a home project), I'm a bit security conscious and I'd like to run X as non-root. I already checked http://ift.tt/14PS0so, but it seems dated: running X with -nohwaccess complains:

/usr/bin/Xorg vt8 -retro -sharevts -nohwaccess -logfile /tmp/Xorg.U.log :1

...

Fatal server error:
(EE) Unrecognized option: -nohwaccess

If I take the flag off, it starts but fails right away:

Loading extension GLX
xf86EnableIOPorts: failed to set IOPL for I/O (Operation not permitted)

It seems like a permission problem, but I've set all the rights mentioned in the wiki article:

videoplayer@yuunagi:/usr/bin$ ls -la /dev/tty8
crw-rw---- 1 videoplayer root 4, 8  1月 13 02:09 /dev/tty8 

/dev/event/* have o+rw set,

The user videoplayer belongs to both video and audio groups:

videoplayer@yuunagi:/usr/bin$ cat /etc/group | grep videoplayer
audio:x:29:videoplayer
video:x:44:videoplayer
videoplayer:x:999:

What I am missing here?

Edit: Btw. before anybody points it out: I have KMS enabled. Kernel log says so, (open-source Radeon drivers with DRM in function) and X.org logs says so: [KMS] Kernel modesetting enabled.