I've made a lot of Belgian beers the "low-pitch, hot-ferment" method, and none of them were anywhere near as good as that oaked BDS was. YMMV, but I haven't found underpitching to do anything but make my beer worse.
I've kinda been wondering if this is an either-or situation. I.e., if you underpitch can you get away with lower fermentation temps, but still retain the phenol character? And if so, do you gain any other benefits (i.e., can you get more phenol with less fusel)?
I think you're best off tweaking one variable at a time. Stressing the yeast one way may yield positive results, but its a balancing act. Too much stress will inevitably make bad beer.
I also err on the lower side of ferm temp for most beers (or at least starting low with a controlled ramp-up). When I work on the higher end, I have a difficult time controlling to a setpoint during the peak of heat generation.
Either way, under-pitching and under-oxygenating are methods commonly used by pro's to make excellent beer. It may or may not work in your brewhouse, but its worth investigating.