Oh, all three front panels have used row drivers; in MIDIbox ASIDITY it was a bunch of TO220 NMOSFETS, in MIDIbox FM V2.0 / V2.1 it was a Darlington array, and in this one it's eight TO92 NMOSFETS, they're right next to the orange LEDs in teh middle. Obviously the shift register pins can't sink >1 amp!
But I don't quite understand the issue--MIDIboxes have been using BLMs with this scheme for 15 years. And in fact, since only one row is on at a time, having 8 or 16 rows from each pin of the shift register is just the same as having each shift register pin drive one single LED by itself. That's what the DOUT module is specifically designed for.
You're right about PWM, but I don't use dimming on any of these panels. :) I don't find that it's terribly useful to convey information to the user.