That's a great idea and I must admit at first I thought it looks a little "raw" but after painting it looks real nice. I have seen a lot of good suggestions on the forum in regards to cup holders but just haven't made up my mind as to which one to use. Driving 4 hours last night from Miami to Tampa made me realize that I definitely need to put a cup holder in very soon!
Since I'm not good at welding I have though about getting this one here at Walmart and simply sticking it in the little bag that is right where yours attach to (fits perfectly as I have seen from a different member) and would serve the same purpose as yours:
Sew Many Ways...: Tool Time Tuesday...Cup Holder Sewing Caddy

Only problem, it is a little awkward reaching behind your shoulder while driving so the spot is not ideal. But then again it's absolutely right that a spilled drink would do less damage than a drink spilled over the console and into the electronics!
I'm still a bit mad that they didn't use the cupholder from the Mercedes SLK 320 that pops out below the A/C vent on the middle console! Would have been a lot better than the pesky little thing that pops out where your arm is supposed to rest while driving!