I appreciate what you've accomplished so far!
For my purposes, I would like a replacement for Response Modeler, but would want to see integrated room, boundary, and diffraction simulation.
Unfortunately, the Excel based RM has never worked right on my computer. Pressing buttons results in errors or operations that simply don't run. I'm going to ask Jeff if there's a way to run it w/o the macros.
I've also looked at Unibox and HornResp. The sim on the former stops at 1,000 Hz, so the higher frequency impedance model is missing. HornResp runs to 20 kHz. Below 1 kHz, HornResp, Unibox, and traced measurement agree within ~10% (sample size = 1). The model for voice coil inductance is different in HornResp and it predicts much higher Z values above 1 kHz than traced measurement graphs show.
In the short term, it's probably easier to just measure the drivers in-box and use that.