When I first embarked on this quest to make my led bulbs stop failing, I saw a video of a russian guy that, beyond removing the bul itself, drilled roles on the base of the device, and plugged screws on them to create passive cooling. Not very safe, since the screws have access to the inside of the fixture, and can eventually touch the wires and become live, I wouldn't personally do it myself.

As for drilling holes on the bulb itself, I'm pretty sure it would not reduce the temperature as much as simply removing it, and in my experience, the luminosity is even better without those cheap plastic bulbs anyway.