Because I may have to have a virtical divider between my pc motherboard and my xbox motherboard. I want to put my xbox inside my pc. I also want it to be a very clean install.
I see what your goal is, and it's very noble! Making a mod that's clean seperates the men from the french;)
I would think that your idea would work if you kept it pretty simple. A ribbon is good thinking, but I would have to second think the added length envloved by adding ribbon. If you kept it short (say, an inch or so. Long enough to bend the card parallel to the Mobo) I'd say it's worth a try.
Another way to look at this would be to make your own socket "L". If you know how to trace out a board, this could turn out pretty clean! Say, take an old AGP card and saw off the connector, then fix it 90-degrees on the sawed off end. I'd say you may need some ckt trace experience in case you need to add a trace if one of the leads needs added to you "adapter L".
But to warn ya...you'll have to devise some method to get the signal out from the card out of the box because you won't be able to use a standard case's PCI tray's out back. Also, you'll have to bend it south because the CPU is North...and the guts of the AGP card is on the south-end making the space savings pretty minimal. Ahhhh...the ribbon is starting to sound like the only way to get this right :p
How about simply purchasing a larger case? With huge cases like a CM stacker, you could fit a small imigrant family in there with you mod...