That's why the CDS cell and the #49 bulb worked so well the attack and decay are limited
by filament heating and cooling.
I'm aware of all the various opto isolator, that parts bin has about 15 different parts.
The Jfet based parts might work well. I've used the 4n25 and 26 parts in attenuators as well.
FYI a common Jfet works well too, generally as a series device.