I second; don't use filament bulbs for such a safety critical application.I would think that, to avoid having to climb up the tower and replace the bulbs, you would use a longer lasting form of light such as LED bulbs rather than incandescent.
You could control the brightness with a controller such as this with the DC brightness level signal provided by a couple of 555 timers circuits.
Does that sound like something you could put together if the circuit schematic for the timer was provided for you?
It wouldn't be that difficult to sum in a slow sinewave to the error amplifier of many common types of PWM chip.
A bit of research might dig up an off the shelf LED driver with an identifiable PWM chip. The fed in sinewave periodically makes the PSU think its overvolting - so it dims.
Various options for generating slow sinewaves have been discussed on one of these forums recently.
The slow up/down of sinewave control would be the least harsh on filament bulbs - but I'd still go for LEDs.