Very interesting. I chose the Cool Rails because people here on Talkbass (and/or possibly the Seymour Duncan forum) recommended it for the Bronco and also specifically warned against the Hot Rails because it was "too hot" for bass. But after hearing the Cool Rails in my Bronco I don't think those people can possibly have heard the Cool Rails inside a Bronco. People on the internet recommending stuff they've never tried, nothing new there I guess.
What you're saying makes a lot of sense to me after actually testing Bronco+CoolRails. It sounds anemic. Will the low frequency response improve with the Hot Rails too or will it just be generally... hotter? Because the low frequency extension with the CoolRails is pretty useless with my Bronco, no matter how I set the pickup height. I actually liked the sound better with the stock cheapo ceramic strat pickup. Unfortunately it picked up far too much noise to be even remotely usable and I don't think I can be bothered with the full copper foil treatment here. It will have to be a noise cancelling pickup or nothing.
Honestly, the ONLY use can see for my Bronco except unlugged noodling is playing the upper register muted pick style as a kinda baritone for tic-tac doubling. But it's lacking a bit of clarity in the attack for this and I don't really need it as I've already got a baritone + several far better short scales. I was probably an idiot to buy the Bronco. Impulse buy online to reach the free shipping limit from Thomann, lol. I figured it could be a fun mod project but unfortunately it turned out to be a waste of time and money.
BUT, if I can improve it with another quick pickup change I might just do it.