your legs are the strongest - climb with your legs, not hands. So use a pair of ascenders (one for the harness, one for the leg(s). If you use a 4:1, you have to use your arms. A 3rd ascender on a separate halyard, as safety. No need for extra help. Even in a fractional rig, you can use the jib halyard as safety line (the worst case, you fall a few feet).
I agree, and have gone up several times this way (mostly birdproofing missions). My home-made rig is SLIGHTLY different than this... instead of your two ascenders, I use one ascender, and one grigri... by alternating between standing on a strap attached to the ascender, and "sitting" in a harness hooked to the grigri, I can inchworm my way up under my own power... legs are strong... arms are weak. Then when I'm ready to come down, I can ditch my foot-strap & ascender up there, with just my harness attached to the grigri, I can belay myself back down. Yes, all of this should be done with a second/separate belay system as backup as well.
I also don't CLIMB up the halyard directly... I use a halyard to hoist up a static climbing rope with nobody on it first... then it is fixed there, and I ascend the climbing rope. All of the equipment (halyard, climbing rope, carabiners, harness, ascender, grigri) is closely inspected for wear, damage, safety before every use.
While having an assistant may help with safety in some ways, there is also a plus side to not having a helper anywhere near the danger-zone directly below me where I could drop a tool, etc.