In my (very limited) experience, s/h is exactly what you want to do for a rootless oncidium alliance plant! I put my first oncidium in s/h only a couple of weeks ago, and I'm talking about rootless, heavily neglected, definitely on its way out plant. Actually, more than one... or two
. Yeah, I'm not good with onciciums. Well, ALL of them sprouted new growth within a couple of days! I'm not kidding. I'm still watching these babies since my experiment is so new, but they all seem to be on their way to recovery, and the speed of the progress is just unbelievable.
I'm sure your plant will be just fine