While I agree with Rwh909r regarding the high chance of getting your cloacked site de-indexed once Google catches you (although I must stress that it was posted in Black Hat SEO section and most of the strategies discussed here involve this risk - it's simply something you need to deal with), I strongly disagree with this bit:
The main site will contain no elements that are against Google's guidelines (cloacking will take place only on the redirect site), therefore there's no reason for Google to de-index you. If this was true then what would stop me from creating hundreds of cloaked redirect sites, pointing them to my competitors' sites, reporting them to Google and getting them de-indexed?
An exception to this is perhaps if your redirect site and your main site share the same IP address - in this case it's reasonable to expect that both of those sites are yours and Google might go ahead and de-index you.