The Gentoo Installer project aims to create an widely extensible install engine that allows for a diverse set of attended and un-attended install options. All functionality will exist in the backend, exposed through a stable API. Planned front ends include text, gtk2, fully automated, and web-based interfaces.
This has been mentioned multiple times over the years, but was shot down by many on the Gentoo forums as defeating the whole purpose of Gentoo. Not really. It you use an installer, you still have to compile the packages and get to customize your system to the max.
I hope they follow through with a good release in the near future.