Hey Stephan. Actually Rebel Yell was my first choice. The EQ and output is almost exactly similar to the 59/Custom Hybrid, but I thot since the extra scale length and ebony frets of the ML-1 would add some brightness, I want to go with a pickup that has less top end.
HAHA, that's the first time I've ever been called Stephan!
Well, the EQ graphs on the BKP site only tell part of the story. The Crawler is apparently a dark and very beefy pickup with loads of center mids.
The Rebel Yell is an interesting pickup. I wouldn't say it is lots of treble so much as it has high mids and very extensive harmonics. There really isn't a defined CUT at any one frequency but rather, it has a harmonic evenness which is very balanced and nice. The lack of low mids and the tight lows definitely make for a brighter overall tonality though.
The A-Bomb, by comparison, has more treble but the hotter wind adds low end which warms up the sound making it darker and phatter. But, definitely way more of a cut in the treble than the Rebel Yell anyhow. If you are wanting to go darker, I can't help but think something like an Abraxas, VHII, or Holy Diver? I only can speak definitively on pickups I have owned and used but I would not be surprised of others mentioned these options as they are fairly common around here.
This being said, you'll have to try the guitar out first but I suspect the construction likely will yield a result that is wide but lacking in the mids so something with mids will probably be your best bet. Holy Diver? Rebel Yell? It's a question of how open you want. Crawler may work as well, depending on the balance between highs and lows. But, with the mahogany I doubt you're going to have an instrument with top end only like an Ibanez or Jackson style super strat.