I have used HMC's with scales and without, and have never really formed a preference for one way or another. Yes the machines with scales were accurate, but so were the machines without. They were also more work to keep running reliably than the machines without scales. For the type of work we were doing it made almost zero difference in quality. A machine that is geometrically in square and straight, with recently pitch comped screws without backlash is plenty accurate in a climate controlled shop without scales. It takes many many many hours of hard abuse without lube to ruin the screws in a Makino, Mori or Okuma. We had a Mori with grease lube, that had well over a thousand hours with the grease pump turned off. Still could interpolate a circle within .0002", still was able to accurately located features in the entire envelope. Mind you it had scales, but when we had it evaluated, the first thing we did was turn the scales off, it performed just as well without the scales as it did with them. We had bought it used and nobody put two and two together that it wasn't using grease for about a year of use. Previous owners had turned it off.
I would be curious what your experience was without scales that makes you think you need them.