For an example of what I was saying about the plain E,
here is what a plain gut E string looks like, that's meant to be useful with a bow, at a
light gauge. Meanwhile, when Mark Gollihur measured a Lenzner (as an example of one that's really meant more for pizz/slap playing when it comes to having the plain gut E), it was ~4.6mm—that's a heavy gauge plain gut A, you can even order one just like that from Aquila (not listed on the historical bass strings page, but when you look at the full catalogue of all the unsplit lamb gut, it's right there), and Pure Corde has a 4.5mm A.
And people still usually describe them as sounding mostly like a kick drum that changes notes, with very little actual definition and nearly nonexistent sustain. Some slap players love them just for that, but for any more standard jazz stuff, you'd probably be better off with a wound E or keeping a steel E.
EDIT:
Here's a fun example from another talkbass member with everything except the B string being plain gut.
I know everyone raves about Gamuts etc, but budget -wise Gotz and Lenzner are very capable strings (I used them for the first 3 or 4 years of my string journey. I now use handmade Toro strings from Italy... made by cousins of my maternal grandfather, to boot)
Out of Salle, right? I know they make tennis strings too. I've thought about them a few times but I'm thinking I'll probably order my next set from Aquila for the instrument I've got getting worked on right now. Certainly wouldn't mind to go and visit, though, some of my favourite wines come out of Abruzzo.