the magnetic ES balanced output (either 1/4" TRS or lo-Z XLR) is
significantly hotter than a standard unbalanced signal (1/4" TS cable),
so i'm unclear on what you're referring to, in terms of 'half-gain balanced output'
If you plug any standard guitar, like my Larrivee, or a Taylor with the new ES2 system with a standard 1/4" TS cable into an amp , board, or wireless, you are going to get a fairly standard gain signal. Swap it for an ES1 equipped guitar with a TS cable, and the signal drops to about half gain. A TRS cable with a transforming adapter to a standard 1/4" TS plug will bring the gain back up, but a bit hotter as you say. The 1/2 gain signal is a serious problem when you're running in a band setting, so the TRS with a transforming adapter is required to run through a pedalboard or the like and have a signal comparable to the rest of the band. The problem with a wireless is that it doesn't have a balanced TRS plug, so it's getting a half gain signal, rendering it unusable.