I haven't actually, but I know a bit about the subject. There's a woman on eBay that sells coating called "DyePress." Supposedly she has clients that have had good success with white leather. Here's the link to her eBay site. I might contact her and see if the coating would be a good fit for you.
http://www.ebay.com/usr/dyepress
My guess is the process might take awhile to figure out, but the results can be amazing.