The backing bar not appearing on the drawing and, WPS joint scetch may confuse some that are used to seeing them that way.
In theory, here is what I am thinking:
I think your current joint designation is B-U2a-GF. Assuming that it is utilizing the root opening of 1/4", and included angle of 45 degrees.
If the joint designation B-U2-GF is used, then the root opening will close up to zero. (If that is what you prefer) "That 1/4" lost will need to be made up some where." Keep the root face at 1/8" to 3/16" that way it could still be considered (backing) just in a different way. The parent metal is you backing as opposed to an external, then removed backing. Eliminating that step. Backgouging will still need to be perfomed, and the back weld put in place. Assuming the welder fills the angle side of the root first.
As far as the difference in included angle. B-U2a-GF with 45 degrees, and B-U2-GF with 60 degrees.
B-U2a-GF is given a + 10 degree tolerance. So I see 55 degrees max. B-U2-GF has a - 5 degree tolerance. So I see 55 degrees min. Both are based on the as fit up conditions. Now I know that it is slim to none that these values are going to be exact in the field. In theory 55 degrees look good on paper.
Generally thinking; If the included angle does open up, then more weld metal will need to be deposited. Certainly an increase in the aspect of time. If the steps of attaching/removing the backing are eliminated, then it might either balance or offset that time. Hopefully offset to the good.
I am not too sure how deep the joint is going. I think it would be nicer to have more room to move, then feel confined in a tighter joint. Assuming that there is no nozzle, on you self shielded FCAW gun. Would certainly hate to touch out the contact tip on accident. OOPS. "Clean up in joint 123" : (
Just my thoughts.
You indicated "...The feild forman says that they are required to use backing bars on all CJP for this job. Im not sure if its in the specs or that just something the site inspectors requiring?..."
Is it possible the requirement is written that all CJP welds shall be welded with backing ?
If that is the case, joints welded from both sides after backgouging are consindered welding with backing. Maybe the requirement that is in the project specifications need to be looked at again just to make sure.
Gerald