Thanks to the useful and detailed info on the wiki; I made my own keyboard layout. It's mostly based on vi_'s keymap but I added on the fourth-level: dead ` on F-key, dead ´ on G-key, dead ¨ on .:-key. Also I re-fixed the Euro-character he removed.

Still, it sucks that qt-application refuse to follow xkbmap, or partially. It doesn't follow all fourth-level keys, however it DOES follow the dead-characters I added on the above mentioned keys... Weird! =/

Edit:
According to Mentalist, some programms use KP_delete. to tackle this once and forever, I was thinking of some construction like this

[CODE
key <DEL> {[ KP_Delete ] };
key <KPDL> {[ Delete ] };
[/CODE]

This doesn't work as expected, unfortunately
Any ideas?