With bsdimp's great finds, it would be a big help if one of the MAME dev people could convert the Rainbow driver to a modern, slot based format. This would help other contributors to find their way around more easily. The Rainbow is one of those drivers that has attracted different people over the years, and the dual processor, extendable format is really a showcase for what MAME can do.
The conversion is certainly beyond my scope, that's why I'm asking "pretty please"