Thanks Telerocker! I emailed the team and Ben replied, and between the two of you, I'm pretty convinced I'll be fine with the Mules.
Ben said that while he couldn't be sure I'd be happy, he was confident that the Mules work in all kinds of guitars. That he said that rather than "definitely do not put a Mule in a bright guitar" was reassuring.
He also mentioned that the Abraxas isn't that much of an extra kick compared to the Mule. Given that it's always described as a "Mule on steroids", I was expecting it to be a Mule-and-a-half kind of situation, but Ben described it as only being 10-15% hotter. So if it does turn out that the Mule doesn't work, I'll definitely go for the Abraxas set. But I'm feeling fairly confident that the Mule will be fine, now.