Okay, I understand your point. If strings don't work you for, maybe that extra inch for the scale length could do to trick.
May I ask you, what is your budget? I see you where thinking about Sandberg, they are in the 1200 - 2200 bucks range, though your budget could be somewhere around 1500.
I would like to suggest the Ibanez BTB Premium 1405e. This bass guitar has a 35 inch scale length and a neck through design. Very good for tuning down. I think you could get some mighty lows with that bass if you keep your .140 Low B string and then tune it to Bb

Check it out!!
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This is a well designed 5-string bass.
But instead of blindly picking a bass that is someone else's favorite, I will give some design criteria to look for, which the above bass has:
1) At least a three-piece neck for stability and damping of resonances (dead notes).
2) 2 (B&E) + 3 (ADG) tuner arrangement so the B string doesn't bind over the nut or around the tuner, but has enough space for the string leader to tune the B string smoothly.
3) Lightweight Hipshot, Gotoh or Schaller tuners.
4) The "neck" pickup in proportionally the same position as the D-G segment of a Precision bass pickup to get the proper balance of fundamental and overtones on the B string.
5) Longer upper horn to balance the bass against neck dive.
6) Clean broad-band hum-cancelling electronics, whether active or passive, because Jazz growl doesn't necessarily equal clean when it gets to the B string and P thump doesn't necessarily mean solid fundamental and sustain.
There are many basses on the market that meet these criteria, from my $279 on sale Ibanez SRA305 to the multi-thousand dollar offerings of Dingwall and Little.
Shop a lot. Play a lot. If you see one you like, put it down and walk away from it and come back a couple of days later to see if you feel the same way about it then.
Notice I did not say anything about nut width, bridge spacing, scaling, neck contour or body wood. This is because these are all personal preferences and good basses are out there with all variations on these themes.
I will only add, because of the downtuning, that yes, the 35 inch scale may be beneficial, but not necessary for standard tuning.