All a bit confusing since we have no idea which a/c we are talking about, but I think the only thing that could affect RVSM would be if the particular A/P required an FMC to function in basic height hold.
King - into which piece of kit are you planning on entering waypoints via lat and long and exactly what do you expect to get out of it afterwards?
As type 1106 says, you are already 'lost' before the failure
