It's been said already, and probably now overlooked: almost ANY bass with a *proper setup* for B/E/A/D, with the right strings, will do.
A new nut might be needed for a larger diameter set, but it's a cheap part at under $10 for plastic, $15 for graphite, and hell, you can even go brass if you want. DR DDT strings are made specifically for drop-down tuning and have served me very well for the past several years, and I tailored my basses' B/E/A/D setups around them (for me, .125s). A replacement bridge is also cheap enough if you want to maintain the originality of whatever bass you end up buying if you have to tap out the holes ever-so-slightly for larger strings.
And as far as the "don't-dare-do-it-to-a-Ric" frame of minds, I've personally played two early-'70s 4001s that were set up for B/E/A/D and sludgemetal. One had an original bridge, the other a Badass version 1, and both did the job quite well because they were set up for that tuning. Don't get me wrong, I'm all about the sanctity of Rics, especially the 70s versions, but it's not like you're tatooing the headstocks or reshaping the body if you go for a lower tuning, and it can be undone later with another proper setup for "normal" E/A/D/G.