I like the ST-E3-RT the way it is, no need for a bulky AF assist light.
I would greatly prefer an AF-assist light built into a Canon flash commander! I occasionally run into shooting situations where I am no able to AF without the ST-E2 AF-asist light.
Really up to date would be an ST-E4 with radio wireless and a non-bulky, but rather tiny, industry-standard IR-laser-diode as AF assist illuminator ... similar to the (Non-IR) laser-AF-assist seen already years ago on the Sony F717, F828, V1 to V3 cameras.
And in addition, finally a Canon wireless-radio RT-receiver to also control 580/II and 430/II speedlites via radio wireless. As long as Canon does not offer tjhose - and at a VERY reasonable price [around 50 USD a piece!] - I will NOT buy into the Canon wireless RT-system.