My Spector Rebop is a 35" scale, has the tighest B I've ever played. The Peavey Grind 5 has a tight B at 35" Neckthru. The Epi T-bird Pro-V has a 34" scale neckthru with a tight B. A B-string isn't inherently floppy, it just needs good design. Not just taking a 4 string model, widening the neck & slapping one on.
Also, be careful with "just put thicker strings on". Sometimes the extra thickness will require you to raise the string up higher to avoid fret buzz and then it will just feel fat & awkward (and will resonate really dull) compared to the rest of the strings.
My suggestion: Go to a store where they have a guitar tech who can do on-the-fly adjustments to any bass you pick up. Try them out & talk to the tech. My tech's taken some 34" Ibanez basses with POOR Bs and made them much more playable through 5mins on his bench before purchasing.
To reiterate what I said in post#39 "the only thing that does matter is the scale of the bass, and the type/gauge of the string". 34" scale is 34" no matter what bass it's on, and the same with 35" scale basses. The bass brand does not matter (unless it's total junk), and FWIW - I've worked on my own Ibby SR's for many years, and there is nothing you can tweek from the stock settings to make for a tighter B except for changing string type/gauge ..... or using a neck stretcher.
I'd love to try a Dingwall like others have mentioned, but don't think I could get use to fanned frets.