HLG and ACES is tricky. ODTs (as the name implies) produce display referred output, whereas HLG is (notionally, at least) scene referred. The picture rendering in HLG is supposed to happen in the display, whereas in ACES it happens in the combination of RRT and ODT.
All you can really do is create a transform for an HLG display of e.g. 1000nits, based on the ST.2084 1000nit ODT, and use the maths from ITU-R BT.2390-0 to add a PQ to HLG conversion so that (on that display at least) your HLG ODT produces the same display luminance in HLG mode as the PQ one does in PQ mode.