Good few years back folks were trying to use water jackets around the bulb- worked pretty well, once you got the electrics waterproof. The water would then drain to waste. Water volume was an issue, unless you were off muni supply. Don't see commercially marketed fixtures, so I'm guessing it wasn't ready for prime time.

Only issue that I see- isn't a relatively small sealed tank going to heat up pretty bad? The pumps will equalize the temp throughout the tank, but they're not going to actually remove any heat.

Seems like you'd need some kind of heat exchanger to cool the water, in order to prevent boil-over.

Prob also have to vent the tank- temp changes=volume changes. Not a huge volume increase before water vaporizes, but still there... and once vaporized, pressure builds pretty quick. Seems like you'd want a blow-off. ( To avoid blow-up).