Share resources with NTFS
I cringe at this suggestion, however with most people slowly transitioning over from Windows on the same machine could there be an option to include your locally installed Windows Steam folder? Especially if you have sprung for a SSD, games are getting huge, and not needing them installed twice would be a large benefit.
The performance hit with NTFS-3g might make some games unplayable depending on the system, but I think the bigger issue would be on Valve's side ensuring that two OS's writing to the same files play nice with each other.
Any additional thoughts on the topic, or start a discussion to try to get attention to this suggestion?