You are wrong there Mike. You are making an assumption that people shoot using RAW to correct their mistakes in post-processing. The fact is most people use RAW because the in-camera processing to produce JPGs is nowhere near as good as the better of the RAW processing/conversion tools.
I prefer to process from RAW to TIF which will re-size far better than any JPG. My choice of RAW is based on producing the best possible image quality for high-gloss magazines and they prefer a 20-30mb TIF anyway. I produce JPG from the TIF for web use. I in no way regard myself as a sloppy professional.
If you want to record the accurate WB for shooting the scene in RAW, use a grey card or an Expodisk (my preferred method) and use that shot to apply WB in your conversion, by shot or by batch.
i didn't call y ou sloppy, i said that raw is making photographers sloppy at what they should be doing.
there are exceptions, like fine art work or landscapes where you need as much data as you can. i've had 2 page spreads printed in national (usa) magazines from my 10d w/ no problems. ive also recently had a fine art paper print 22.5x30" from a 1d that looks stunning. point is... you should shoot as best you can and leave your raw workflow for things which either you can't control or because you need tiff files anyway.
i work at a pro lab (i do IT there) - we are a jpg workflow. we've done the comparisons... for almost everything up to 20x30 you will be hard pressed to tell the difference between a jpg and raw file. you can doubt me if you want... but w/ several million dollars in scanners and printers, im not making these judgements from my home inkjet printer.
also - a lot of shooters shoot raw because they never had a film slr and don't fully understand exposure, exposure compensation, sunny 16 rules, etc... but do understand how image editing programs work. likewise, most of these instances will never yield a print bigger then 11x14. if a big business hires you to shoot headshots of all 400 of their employees for 5x7 prints, are you going to shoot raw? if you do... you've just added a few extra hours to your workflow. if you can do a custom white balance and use a light meter, you should have no issue shooting jpg and printing w/ almost no retouch other then glasses glare or a pimple.
i also don't agree w/ your method for custom white balance. the canon dslr will see a white card better then grey. if you shoot a white card and tell the camera this is 255 255 255 white, it knows it and you'll see a HUGE difference on the next shot you take. thats one less thing you need to do in the raw workflow. if you can do it in camera, do it. thats what you buy them for.