DMX Control - 50W COB LED
How about 4: 

Use the PWM signal from the DMX controller to drive a dimmable LED driver?

Just make sure you have a pull-up resistor if your DMX controller is open-drain, and that the frequencies and voltage levels are compatible with your LED driver.

Product recommendations are off-topic here, but there are plenty of commercial constant current drivers with analog and PWM input for dimming. 

Some comments with regards to your question...

1 - Your boost converter won't like being driven by a PWM signal.

2 - That doesn't make sense as it is not even a full solution, you just delegated the issue to another design step.

3 - Building something from scratch is a decent option.