Well I have a bit of experience with the brown sound and a few pickups, so I'm going to say some things
1) You DON'T need a high output pickup with a Mesa Boogie Roadster. The amp has more than enough gain for almost any aplication, even if you use single coils. So choose your pickup by the tone and not output.
2) You WON'T get any closer to the brown sound without a MARSHALL and a 4x12 with GREENBACKS. PERIOD.
3) The VHII is WAY more versatile than only early VH tones, and it has lots of gain even being a "vintage hot" pup, it saturates an amp really well, pairing with other contemporary pickups such as the DSD (another good option for brown tones) and so... I own one and I can say. I used to run it through a Orange ppc 2x12 and a MEsa Mark III, and the tone was MASSIVE. I could play everything from blues (in the clean/crunch channel) to Dream Theater with the same guitar with only a tube screamer in the front, and it was not because of the lack of gain, but to tight up the bass a bit. The VHII has a huge bass response and has lots of punch too.
I wound't get a Crawler because of its low mids, maybe it's not going to pair with the Mesa as it has TONS of it too.. maybe it can sound a bit muddy in that region even thoug BKPs are clear and defined, the crawler has a vintage voicing low end that is a bit loose. I think the RY and the VHII are nice options for a one humbucker guitar.