Do you think it can be interfaced with the NeXT stuff?
I'll let the technical questions to be answered by the Hatari team but it definitely can by interfaced. Some years ago I took its DSP sources and integrated it into my DSP simulator: https://github.com/mikrosk/cute56 ... easy peasy.
The level of emulation precision is excellent (even for such aged source!), the main source of problems in Hatari comes from CPU <-> DSP sync.