I have finally nailed a Paul Jackson tone, but the solution wasn't found in single pedal. I tried the Nobels ODR-1X, and while it added some grit (and I loved it as a bass overdrive), I realised that grit was not the key. Here's where I landed:
1) Compressor. I have my Empress Bass Compressor set to at 4:1 with a moderately fast attack, medium release and 50% mix to add punch but keep dynamics.
2) EQ. I have my Source Audio EQ2 with a channel at the beginning of my chain and the second channel at the end. The first channel adds low-mid punch and cuts excess high-end, while the second channel rounds the output with a vintage tone.
3) B15 Emulation. I have a Broughton Fliptop which provides tube warmth, enough gain to be on the edge of breaking up, and cab character at the end of the chain.
In combination, I have punch, dynamics, and a round vintage tone with tube warmth and B15 emulation. It's as close as I can imagine getting to a Paul Jackson tone with pedals - and its a real treat to play through.
Now I just need to learn to play like Paul Jackson!
If anyone wants exact settings I've used, I'd be happy to share.