We have an Alpha script for Reason and the Base here:
There's a README that tells you where to install, and a PNG file that describes the functions of the Base controls.
These features are hardly set in stone. Hell, some aren't even implemented yet!
The mappings for the sliders are based on a Propellerheads example template. We haven't dug into that wormhole yet, we just wanted to get things functioning.
In case you are curious about which 8 modes/scales are implemented, we have:
There's many more available. You can edit line 40 in Base.lua and put whatever 8 scales you are interested in as the first 8 items in the "scalenames" array.