Interesting!! Gotta say though, unless the TOM you tested was a custom item - you didn't test any steel bridges : tune-a-matics by most makers have a cast zinc-like-substance body and brass saddles. Tru-Arc does a stainless rocking bar bridge, but the stock Gretsch Item is nickel plated brass.
Which is kind of in line with my findings : the bridges with the most real treble content regardless of other frequencies or emphasis were brass or had brass saddles. I've had two steel Tru-Arcs, and surprisingly, they're less bright than you'd think - they're extremely balanced across the guitar's frequency range with no real emphasis on any particular side. The brass bridges I've tried had more agressive treble.
Like Smiert, I hear the Bigsby bridges as trebly too, but maybe more as "thin", because they seem to take the low end out of the wound strings more than anything else, and they're not big on sustain so the treble strings can seem plinky.
With bridges and pickups, I think it's like a lot of music/EQ related things : emphasis on certain frequencies can make it seem as if the other ones aren't there.
Funny too how you describe Franz pickups as having "no bass" - very well possible compared to other pickups, and the emphasis with them seems to be midrange and treble (in guitar speak - in the bigger scheme of things electric guitar is really almost all midrange)
But my own experience with Franzes is on a giant X175, and the neck pickup on that guitar certainly doesn't lack bass, quite the opposite actually. And then my DeArmonds are on an old Starfire, small, thin guitar in comparison, and predictably, it has less low end than the X175. But that probably has more to do with the guitars than with the pickups.
But back to your current situation : I think a different set of regular P90's might very well do the trick. I have a very (very!) nice Gibson ES175 copy that has a pair of Duncan Antiquities on it. And while they sound good, and particularly the neck pickup on that guitar does the archtypal smoky Gibson archtop tone very well, I'm a little frustrated with them as well. They seem to have so much emphasis on the midrange that the treble frequencies suffer. I've already replaced the magnets with Alnico V, and that helped a little bit, but they're still not lively and twangy enough for me. I keep telling myself "well, you have the Guilds and the telecasters for twang, you got this guitar bc you wanted a Gibson", but then reading your experience with the Duncans gets me to think I might like a different pickup in that guitar more.
I have a set of Lollars in a tele, and even realising the guitars don't compare at all, the lollars (their 50's wind) do seem livelier and brighter, and less plump and woody-all midrange.
I went ahead and ordered one of those cheap staple knockoffs in Germany for the neck position of the ES175 copy, it should be here next week, I'll let you know how I get on with it!
One of the joys of the DeArmond is a "hollow mid", e.g. a Fender type EQ curve with low end and high end but a scooped mid. I'm greedy and I want more top end but no less bottom end. My compromise is I'll sacrifice the middle.
