I'd personally love to see a ROM that focuses less on customizations and adding their own "flavor" to Android, and just attempts to track AOSP as closely as possible while supporting as many devices as possible, so users whose devices are no longer supported by their manufactures (or who just don't like the customizations the manufacturers have made to the UX) can continue enjoying the latest Android improvements in…
If I'm not mistaken, there are a decent number of small projects that just rebuild AOSP, with little real momentum behind them.