Re: Why are minihums so relatively unpopular?
Let me start by saying that because something is "unpopular" doesn't mean it's necessary bad.
I have a mini in my thinline tele, and personally, I think it's a great sounding pickup. (It's the Antiquity).
I removed the ring, and mounted it to my pickguard, but the point is, it sounds great ... I think both the minis and the Firebird pickups fit the tone profile of a tele very well, and for me, they are an improvement over the regular neck tele pickup, but still retain a little of that tone. Even though they are different pickups, I think for the same reason, Firebird pickups are sometimes used in the neck position on teles. One of my good friends has used that setup for years.
I tried a Seth in a tele neck position, and never could get the balance right between the two pickups ...
I had the idea of using a mini for quite a while ... it's an idea I got from seeing Richard Thompson's original Ferrington, which has a mini in the neck position, mounted directly to the wood. I figured, if it's good enough for him ...
As far as Firebirds, besides Clapton, who toured with one for a while, another guy I associate with a Firebird is Gatemouth Brown, who played one for years. I think it gave him a tone that was perfect for his type of jazz/ blues.
If there's a point, it's that a mini, or Firebird pickup might be a perfect solution for you. You might arrive at that solution through a long process, and you might find a tone that is a little more unique, but just works.
If you look around at some of the custom builders out there, you'll see them using Charlie Christian pickups (Asher), even horseshoe pickups (Cardinal) ... these pickups were very rarely used just a few years ago, other than as vintage replacements. People are using a greater variety of pickups than ever, and that's a good thing.