Gibson acoustics had adjustable saddles for many years in the 1960s. My own favourite guitar is my 1963 Epiphone Texan, which is basically a Gibson J45 with different trim, made in Kalamazoo. It came with an adjustable saddle which I used for years, but I always felt the sound would be better with a proper glued-on rosewood bridge, so I had my local guitar tech make me one, and at the same time fit an L.R. Baggs dual pickup system. The guitar sounds fantastic both acoustically and electrically now, and I have never regretted swapping the original bridge.
For one thing the bridge body was plastic, for another it was only screwed on, and lastly the adjustable saddle meant that only the adjusting screws on the whole bridge assembly were actually involved in moving the guitar top to create the sound. What a terrible design the whole thing was. I believe they were done to appeal to electric players at the time, as the Beatles and one or two other bands were sometimes using acoustics in some of their records. Paul Macartney used a Texan on Yesterday.
Anyway, I really believe that a good acoustic needs a fixed, glued bridge with no adjustable saddle. The other thing of course was that I couldn't have an undersaddle pickup put in until it had a proper bridge on. When the guitar was built there was no such thing as an undersaddle pickup.
A couple of weeks ago I bought a secondhand Avalon Silver Series guitar which I'm really getting to like. I've worked on the action and it's now pretty good, but I do feel that it's a bit stiff to play, particularly when I compare it to my Texan, which is very easy, although the action is no lower. Is the scale length longer on the Avalon? I believe that would make the strings tighter wouldn't it, because they have to be tightened more to get them up to concert pitch. Or is my logic a bit flawed?