Support for Multi-core/multi-processor would be a "real" big upgrade.
but that would mean changing the fundamental OS core. not sure that makes sense as far as time put in and compatibility. maybe a library that would allow additional cores/cpus & Programmable GPU's to be used as some form of "slave" cpu for specific functions? IDK. just my $.02 as I have no idea if it would even be practical in regards to memory usage and bandwidth... etc.