I can see that the trunk you propose to keep has some nice gentle bends but side views show that it moves quiet strongly away from the side with the scar. Bonsai look far better when the apex comes slightly forward so using tat as the main trunk really limits the front to the side without scar.
It also looks like that trunk (and probably the others too) has some quite long internodes which may make getting enough branches to fill the design difficult. The options then become hard cut back and regrow the whole to or graft branches into desirable places.
Long internodes are a common feature of commercial maples as they are grown as quick as possible. In my experience Bloodgood seems to be especially prone to long internodes and less ramification so I've stopped trying to grow bonsai with that cultivar.
I know dead wood, shari and jin are frowned on in deciduous trees but I quite like the look of that scar. If I could find a way to bring a new apex forward I'd try to show that as a feature but if the trunk won't play ball just use the other side or choose another branch as the new trunk line.
Along with removing the extra trunks I think you need to reduce the height of the remaining trunk and branches. Cutting hard seems like a step back but too tall and your bonsai will appear skinny. Harder pruning will also start the ramification process. It is common for commercially grown JM to be chopped way back to just a trunk and branch stubs to get good regrowth suitable for good bonsai.
