As usual, the advice and ideas here are extremely helpful and I am very grateful. I'm a pain when it comes to choosing pickups - it's so much easier giving advice, lol. Anyway, I do feel like I've moved on a bit. There doesn't appear to be much love for the Crawler/Emerald option, Abraxas set or Abraxas/Emerald option here so let's discount those. Although I am tempted by the 'safe' Holydiver/Emerald option, I suspect that if I went that route, I'd spend the next few years kicking myself for not taking a punt on something different. That leaves me with two of my original options and plus an additional one I'll need to investigate further.
VHII set - Phil's explanation of why it sounds 'big' was, as usual, very helpful and well informed. It sounds like it's a bit like having two individual single coils, each with their own character, stuck together in a humbucker and I can see that this might offer some very interesting and 'big' sounds. My experience of P90's is very limited indeed but the one I have played more than just in passing was pretty good. It was more 'dirty' and 'angry' than a traditional humbucker or single coil. It had a rawness about it that was quite appealing so that description does make the bridge sound attractive. If anyone's tried an Emerald neck and VHII neck I'd love to hear how they compare.
Emerald set - I do love the tone of both the bridge and neck versions and I can believe that it may not be as bright as the EQ chart suggests, given that all the BKP models I've tried have been more balanced than expected. The bridge sounds more modern and tighter than the VHII to me and I assume that's why itamar101 is thinking I may prefer the VHII. The Emerald bridge always seems a bit under-represented here so it's hard to get accurate information but again, if there's anyone tried both the Emerald and VHII bridge models, I'd love to learn more about how they compare.
VHII bridge/Emerald neck - Yes, this does seem like a very logical option so I'll ask BKP about it :D