Taking into account the science behind fluorescence is going to help a lot.
The reason why "neon" orange clothes are so bright is because they not only reflect normal orange light, but also absorb UV light and then re-emit it as additional orange visible light, making them brighter than they seem like they "should" be given the visible lighting conditions.
Thus, you can massively cut down on the brightness of neon orange safety clothing relative to everything else in the scene by eliminating UV light from the studio.
Specifically, you could do this by either
1) Putting a UV-filtering gel on your flash, or
2) Using continuous incandescent lights instead of flash.
Either option would remove UV light and therefore cut down the brightness of the safety clothing by a huge amount WITHOUT affecting the brightness of your subject. The UV filter is the better of the two options, because with incandescent, you're making all of the light more orange, which is undermining you by reflecting more normal visible off the clothing. With the filter, you add no additional warm light, while still removing all the fluoresced orange light.
A UV-filter on your lens will NOT work, because by the time the light gets to your lens, it has been converted to visible spectrum already. You have to stop the UV before it hits the clothing.