Pickup that sounds like an Invader but with more clarify? A-Pig. You don' t want something overly bright. Based on what you are saying, the bright tone of the guitar will become strident if you have any pickup that emphasises the already predominant high end. The fact that the Invader works leads me to suspect that the A-Pig or C-Pig will be the best fit.
Other options are juggernaut or holy diver, but the A - Pig is closest. Juggernaut has more string separation and more weight in the midrange, and also has a great clean tone. The advantage with the Juggernauts is the clean, but in the words of Ryan 'fluff' Bruce, "the Juggernaut pickups will punch you in the gut and pour you a cup of coffee at the same time."
So, with them you get more midrange weight, exceptional string to string definition, extremely articulate attack, and a hammering low mid punch.
The disadvantage is that they likely are not as gutteral, angry, and balls to the wall as the warpig. I would anticipate the warpig to be even darker and phatter sounding: Very similar to an Invader but with more articulation, clarity, and string separation. I can't help but think that for a bridge pickup, THIS is what you are looking for.
Holy Diver would work too but think more of a hot rodded 80s hmb. Compared to Warpig (A or C pig), the Juggernaut is more 'progressive' sounding and the Holy Diver is more **cough** vintage.