any chance of adding .hvl and ahx file formats for input to openmpt?
No. They are not sample-based. It would basically require the entire tracker and its GUI to be written to be able to edit them, so you can just as well start using their original tracker instead.
And before you ask for more formats, see: FAQ: Can you add support for SID / SNDH / AHX / AdLib / other formats? (https://wiki.openmpt.org/Manual:_Frequently_Asked_Questions#Can_you_add_support_for_SID_.2F_SNDH_.2F_AHX_.2F_AdLib_.2F_other_formats.3F)