I have no idea whether it is feasible to access the KQ lounge on arrivals and then proceed to exit but I would personally be wary of leaving my luggage for storage at a lounge.
As to checking-in luggage en route at an intermediate point, I have never done it with KQ but I have done it with other airlines and it has never been a problem. Can't see any reason why it should be an issue but perhaps there is somebody with a more direct experience with KQ.
As to what to do on a stopover, you may want to have a look at the
Nairobi connection and stop-overs sticky wiki on the Africa forum if you have not already done so.