Well your right the control file inside mediaportals ipk depends on files for OE 2.0 those files dont install on a oe 1.6 image, note mediaportal does
.
There are several workarrounds:
1 opkg install --force-depends /tmp/enigma2-plugin-extensions-mediaportal_4.3.1_all.ipk
Ignores all deps.
2 Extract mediaportal ipk and put those files in /usr/lib/enigma2/python/Plugins/Extensions/MediaPortal
Or for the very latest version download the zip from
https://github.com/dhwz/MediaPortal , extract files ( folders: .old_files and .psd_backup can be removed not needed) and put those in /usr/lib/enigma2/python/Plugins/Extensions/MediaPortal and reboot
Mediaportal needs the following files on oe 1.6 to work: gst-plugin-flv_0.10.30-r0.1_mipsel.ipk, gst-rtmp-support_2.4-r0_mipsel.ipk, python-html_2.6.7-ml8.3_mipsel.ipk, python-json_2.6.7-ml8.3_mipsel.ipk
Wich are all included in this file MediaportalPackOE1_6.zip
http://www.sat-ulc.eu/attachment.php?attachmentid=108334&d=1367061452
http://www.newnigma2.to/wbb2/attachment.php?attachmentid=20853
You only have to install those files once only mediaportal needs to be updated not the codecs with every version..