From what I understand, HalionONE and Halion Sonic are two radically different engines.
HalionONE is a synth engine (generating its own sounds).
Halion Sonic is a rompler engine (playing back stored sounds).
I don’t think that there’s any direct (or quick) way to make it work together.
The “synthesizers” and “prologue discoveries” sets are presets for an existing VI (both synth engines).
“Elek drums” is a bunch of new sounds for an existing VI (a rompler engine).
“Hypnotic dance”, “Triebwerk”, and “Dark Planet” are new VIs all in themselves.
It could be done, but I think they’d have to record all the notes from all the presets into sound. Not exactly a quick (or cheap) process.
I remember that HALion ONE actually is A Rompler
and that HALion Sonic (SE) / 4 Are actually Rompler And Synth (and Sampler in HALion 4)
I Actually believe that The HALion One Engine is actually the most simple and first version that leaded up to HALion Sonic
It might not be that Hard to convert the “Sound set Synthesizers” to HALion Sonic’s Preset Format Since all of HALion One’s Original Content is also in HALion Sonic (se)
The real question would be why they did not converted it …
The Problem Might be that you have to download A fully new version of the pack and that they think there are a lot of people out there who don’t like to download the full pack again just for that reason
However I would recommend Steinberg to do this anyway since then they will sell the pack better then it will sell now