Right, I've about had it up to here with the Xkb documentation, and with the layout of my shiny new Kinesis Advantage Keyboard. The cursor keys on the kinesis are horribly situated. What I'd like to do is hit a key (AltGr, say) and have it put the keyboard into a navigation mode, with the arrow keys mapped onto WASD and possibly HKJL and, ideally with Home/End, PgUp, PgDn in sensible places as well, then, once I've done, hit the mode switch key again and I can carry on programming. Adding a chording key as well would be good, or, better, arranging things so that if I use the mode switch key as if it were a non-locking key then it'll Do The Right Thing.

For bonus points, making the space bar act like control if I chord with it, but like a space bar otherwise would be good.

Yes, I know I can probably configure my Emacs bindings to get me to this state, but I do use other programs than emacs.

As far as I can tell, this stuff should be possible with Xkb (possibly not the Spacebar bit), I'm just stuck for where to start, and my google-fu has failed me.