A: 

Will have to look into Total Game Control to see if it could do what I would like. Any other answers - or comments to this one - are more than welcome!

peSHIr
Looks like it doesn't based on descriptions on the website. It's more like mapping keyboard macro's to the controls available on one controller. Haven't seen an option of using two controllers to control something; FAQ example for getting two controllers to work for multiplayer action describes running two instances of the software.
peSHIr
Total Game Control has quick email support, but it indeed only maps physical game controllers to keyboard macros. So it is of no use in the question scenario.
peSHIr
+1  A: 

If you want to make it generic to all windows applications I would imagine you have to write your own virtual game controller device driver. This gamedev.net thread seems to hold a few clues. It may also be interesting to have a look at Johnny Chung Lee's Wiimote magic or the Wiimote project. Johnny Chung also links to Managed Library for Nintendo's Wiimote.

The Wii projects should contain enough information if you dig a bit to get you going. I can't really think of any other way, other than perhaps plugging in as a middleware between the application and windows somehow by intercepting messages.

Runeborg
Right. I was thinking exactly along the way of a virtual game controller device driver, but I was hoping something like this must have already come up and such a driver was already available somewhere. Mmm...
peSHIr
Due to lack of better answers, I guess I'll have to accept this one. Thanks very much, Runeborg, for the pointers you gave.
peSHIr