1. You should be able to control the Midi note you want the sample to start play from .for instance if my 808 is in E I should be able to play it from E3 or E4 wherever I desire to pitch across the keys.or if I want to create a instrument and want the A# to be where playback starts from

2. There should be a Glide
3.Also some of your key detections are not accurate , I have a trained ear so I can easily find the proper key .Sometimes you have to use the Relative major or minor

most default samplers in DAW's have these basic functions.I do like some of the things you done