There do exist a few SCSI controllers with an Adaptec AIC-3860Q bridge chip.

I've made an experiment whether it's possible to outsource the SCSI devices from my EISA PC to another PC.
The EISA PC has an Adaptec 2740W (fast-wide SE).
The other PC has an NCR/Symbios/LSI-Logic 875 (ultra-wide SE).

But it was boring to link this computers directly.
I'd like to connect them over a LVD SCSI bus.
So I used two Adaptec 2940U2W in a man-in-the-middle computer.
I connected the 2740W to the first 2940U2W on its SE port.
Then I connected the 875 to the second 2940U2W on its SE port.
Then I linked the LVD ports.

And... it just worked.

Cons:
You should use HDDs only in one computer (due to Operating System disk buffers/cache issues). To avoid this, you can set the one computer to boot from ID x and the other ones from different IDs or to not install the BIOS (works perhaps in DOS only).
Since it is a BUS, performance is shared.
Narrow stays narrow. Speed is remaining too. It means, data width and speed are not being adapted when switching from SE to LVD.
You need an own ID for each HBA (host bus adapter). Except one, your HBAs must be able to be changed from ID 7 to another.
You need to disable the RESET BUS ability on your controllers. Instable bus may hang (happens sometimes with scratched CDs).
Pros:
You can use optical drives in all computers at the same time.
You can increase the distance between SE controller and SE devices to more than 10 meters.

I know there is perhaps no real usage of a method like this.
But in earlier days, I've have had the problem that my Warcraft 2 CD was able to let 3 players play together in a LAN game. When using a common SCSI bus, I was able to play with 6 players, because the CDROM with the same CD just was installed in 2 computers at the same time. There was no copy protection against this!

Edit:
I've just examined what happens when I make a daisy chain with 9 bridges: SCSI: Over how many brigdes can you walk?