You can get around some of these by loading your sample into an oscillator slots wavetable and walking through it with an LFO or an envelope. Although I would also prefer more functionality in the dedicated sampler module.
I think the sampler osc. it’s more suited to load short sounds,like percussive sounds,like kicks or snare tansient/attack,just to improve the wavetabe osc.or drones to use like sub osc.
Best sliders I ever used were on the old Akai s612 rack mount 12 bit sampler. You could pull start and end at the same time, and totally morph the range til you’d exhausted all possibilities for the wave in question. Simple and divine!
It would be nice to have a fully-fledged sampler in Vital.
My suggestion is to integrate an existing open source sampler code to Vital (no need to reinvent the wheel). There is a GitHub open source project called HISE (for VST plug-in development http://www.hise.audio/) which includes sampler that practically has all the necessary features.
My software development skills (C++, JUCE, …) are mainly “Hello World” level, so I have no idea what such an integrating process would require from a talented C++ developer, but surely that would require less work than starting from zero.
I think such a hybrid synth-sampler would be quit a killer app!