Cool idea. Atmospheric attenuation (regardless even if you lase at "transmissible" freqs), would be a major issue. Additionally, beam steering and focusing from 1000km+, and accounting (essentially a variable continuously changing integration) for a high variability in index of refraction would make it possible without a closed-loop feedback of on target strike. Rough ballparks, I mean, the beam power density required would likely far exceed the thermal dissipation rate of any heat pipe, etc, tech I am officially aware of. Space warfare is super fun tho. However, this is a very outdated idea. If anyone like noodling on this stuff, they should DM me. There are far better ideas... unofficially.