There isn’t a 100% straightforward answer to your question because transwaves are really just what you describe: Loop position modulation at a set interval. In order for transwaves to sound nice, the sample file that is being loop-pos modulated needs to be resynthesized outside of your ASR to make sure that each “frame” or “cell” (or evenly distributed number of samples) contains a “waveform” that is in phase with the other “waveforms” contained in the “container” sample file. If you take a regular sample of a crash cymbal and load it into the ASR and then try use the transwave loop modulation on it, it will A) not be in tune when you play it chromatically, and B) sound glitchy and have clicks and pops all over when you modulate the index.
HALion will resynthesize your sample for you and allow you to break it up into as many “pieces” as you like. You can make various adjustments with how it resynthesizes the sample which is the process necessary to make it a compatible wavetable and allow it to be modulated in the way you describe. (this is the part that was done outside of the Ensoniq ASR-10/etc) You can make adjustments to this process in HALion that make it sound less “smooth” which is how transwaves sound. But just due to the nature of wavetables and the goals of the wavetable sound, I don’t think you’ll ever get 100% transwave sounds. But you can certainly get some grit, if that’s what you prefer. Overall there’s too much interpolation and anti-aliasing going on in HALion to get a 100% recreation of transwaves. HALion basically sounds the way transwaves would like to have sounded if the hardware wasn’t so limited on those old Ensoniq machines.
But you can definitely do some very cool things with samples in HALion. I prefer the capabilities of HALion to anything I used to do in my ASR. If you dig in and really play around with it, I have a feeling you’ll enjoy what you can do with it. HALion is a pretty amazing synthesizer.