My UA-5 has a bad input volume knob so I'll be looking at some possibilities since I'll be in there soldering anyway. I think the characteristics of these knobs really suck anyway, at least for my rig the "power band" (-20 to 0dB) is between 3 and 5 oclock making it virtually impossible to balance (esp using JB3 meters). Plus the actual knobs are so small and tucked in next to the XLR's- and the line in one is even harder to access. Maybe they should all go on top of the unit, drill some holes. Worth looking into for sure.
Dial switch with adjust seems to be the best setup, I'm no expert but it doesn't seem like rocket science.