You are talking about two separate things. One is the bad calibration in the stock ICM profile that ships from Lenovo, the other is a lack of accuracy with reds. Fixing the warm look (seems to come out as a yellow tint in later production screens) of the screen is as easy as switching to the standard srgb profile and then reducing red one or two steps in win 7 calibration. The red accuracy issue is tough to fix and really not a big issue unless you do photo editing, and certainly not a big deal considering it's $50 IPS upgrade.
It has nothing to do with the bad calibration in the stock ICM. The stock ICM is the Flexview ICM, it can be easily removed and replaced with the Windows default RGB ICM, but even switching to the Windows default ICM over the stock Flexview one, results in the exact same ULTRA WARM look. Something is inherently wrong with the actual panels.
There's really only two alternatives to solving this issue, number 1 as you mentioned use the Windows 7 Color Calibrator to compensate and bring down the R/G values which will cool down the panel. Problem with this approach is there is an inherent bug in Windows 7 that makes loading images very very slow when you use the Windows 7 Calibrated ICM. Try it and you'll see, if you create a custom ICM through Win 7's color calibration tool, all images loading through Windows Picture Viewer takes 3-4 times as long. This error has never been fixed, rending the Win 7 Color Calibration useless.
The second option to fix the overtly warm IPS panel is to use a Hardware Calibrator such as Pantone, or a Spyder calibrator. But sadly 99% of society do not own these expensive hardware calibrators, so in the end most people will just have to live with the horrible color production of the X220 panels. Sadly without anything to compare it to, most people will never know how horribly skewed their colors really are. The only I noticed is cause I have several Thinkpads and 2 WQHD panels that are properly calibrated.
The last option of fixing this issue is to use the Intel Color Enhancement Software to bring down the R/G values to comp for the warm tone, but since this option is driven by the Intel GFX drivers, it has to load after Windows is booted, resulting in a odd shift in color everytime you load windows or log off.
Regardless, the IPS panels in the X220 series is not something to be envied. It's the manufacturer of the these panels. The Thinkpad Tablet also uses capacitative touch IPS panels, but shows no signs of these color problems. I have the Tablet, so I know.
This issue is widely talked about many Chinese forums, leading to lots of people on these forums exchanging custom X220 ICM profiles to help people who don't own these hardware calibrator fix their display.