This is an interesting question I was wondering if anyone had any experience with. If a website is penalized for a keyword because of excessive spam links pointing to the homepage  with said keyword as the anchor text, could you solve this problem by using a [noindex,follow] tag on the homepage and optimizing a different page for the same keyword?
Penalized website using noindex,follow
google;noindex
Google is pretty vague on how the penguin penalty works from spammy links with keywords so your never an official answer, in fact Google doesn't want people knowing otherwise blackhatters would reverse engineer every-time they got hit.As far as I've learned from clients that I've worked with is that penalties are not just applied to the page that is being linked, the penalty is a global one and normally effects the entire site.So redirecting, or using tactics such as noindex, follow will not work since those links are still present on your link profile.It's also worth pointing out that when people get hit by the likes of Penguin they don't normally just see a drop on their home page, its across the whole site which again would implies its the penalty is set globally, and extends that of just the anchors used. I asked a question about Penguin and Panda many months ago 'When should a webmaster call it a day post Penguin and Panda' Time to do things correctly...Your best of opting to get out of the penalty legality, attempting to look for work-arounds will only work temporary and your be in the same boat, so I believe this would be nonconstructive  and time lost when you could be doing things that will help long term viability. 