T42, in the past all keyboard samplers have come up short..The multisampling you mention is the only way to achieve a good playable sample..It will need more than 8 sample points[unfortunately this is the average limit, and worse yet the limits on sample size..Good luck if you think you can come up with a decent multisampled piano..I have never heard a great user sampled piano yet...The factory has far superior methods and facilities to sample and edit sounds to be playable...I am not sure if great samples can be loaded into today's keyboard samplers and sound as they were designed to play..

For novelty sounds the keyboards sample ok...but how many pot drops or shouts are really needed..

Sorry, I can't share your excitement about keyboard samplers..I have been there, and already know the limitations..
Most of my experiences were on the Ketron X1[considered one of the better samplers]..I also go back to the old Roland samplers..and the Ensoniq Mirage..

Thankfully we don't have to rely on user samples..there are an abundance of sounds available from the factories in expansion cards...and they are done right..