Was doing some back of the envelope math with chatGPT so take it with a grain of salt, but it sounds like in ideal conditions a radiator of 1m square could dissipate 300w. If this is the case, then it seems like you could approach a viable solution if putting stuff in space was free. What i can't figure out is how the cost of launch makes sense and what the benefit over building it on the ground could be

What temperature were you assuming?

Because the amount of energy radiated varies with the temperature to the fourth power (P=εσT^4).

Assuming very good emissivity (ε=0.95) and ~75C (~350K) operating temperature I get 808 W/m2.