The Gallinger looms came with sectional beams. I tried converting to a solid beam. It seemed easy enough, just unscrew the rakes from the solid beam. Surprise! The rakes were nailed through the wooden brake drum, and I had to use a hacksaw to remove the ends of the rakes. I left the tiny eyelets in place, so now we can switch back and forth between sectional and solid beam.
If you send us a good picture of the beam, we may be able to help you. Hopefully, the pins are just friction fit and can be worked out with wiggling. If they are glued, you may have to remove the whole rakes. A photo will help...
I got a Brittany from a friend and connected on-line to get some literature. I can send you copies. The two articles I have still didn't tell me about what I believe is missing on my loom, some sort of tensioner stick... I basically need dimensions so I can make my own. Hopefully you have a similar part on your loom.
Don't know anything about Hazel, but the small Norwood workshop looms were very like the Dorset. I'm not sure they are still in production, but they are available used.
I'm no expert on countermarche looms, but.. judging from the geometry of counterbalanced looms, the shed could be only as tall as the space between the heddle bars and the heddle eye. The reed should be about the same height. The heddle need not be longer than the jacks that control them.
The big looms fold somewhat, but they can be disassembled as well. You would still have to deal with the central "castle" area without disassembly. You sure don't want to mess with the mechanical jacks if you don't have to. The front breast beam assembly and the treadles can be removed, and so can the back beam(s) and brakes. Of course all the shafts come out too. Pretty soon you're down to something two or three brawny teenage boys can lift.