I had a Cove Stiffee running 130mm bolt through forks which sounds exactly what you want. Gave loads of confidence and good for goading you into doing steep stuff (even BikeVerbier alpine steep) whilst still capable for all day rides, particulary with a shorter and lighter fork to steepen things up a bit.
Not the lowest BB around but I don’t like pedal strikes.
Since then I’ve bought one of the new Dialled Prince Alberts which although not so slack has still been blindingly good fun to ride and a better all rounder, albeit a slightly heavier frame. Rode the Transcambrian Way a few weeks ago, Ashton Court, Cwm Carn and Afan all more fun than on my full sussers. Maybe not as quick downhill but lots of hassle free fun.
Thought about a Dialled Alpine or Cotic BeFe?
The other obvious ali frame is the Santa Cruz Chameleon – supremely versatile if a little unforgiving.