Design-wise that would be an improvement, but it most likely would require a redo of the trunk ducts which usually taper down in size as air supplies are taken off the main trunk. That could get costly.Thinking again about the drop in with the existing ducts. How much does the air handler location matter? Right now it’s in the basement on a far gable end. I would think tying it in at a more central - maybe 15-20’ more towards the center of the house may help ?