1. It isn't atmospheric, it is firing with a special weapon directly from orbit.
2. No it shouldn't, you are asking for way too much.
i'm not againts the idea, in the mather of speaking i was posting same idea elier BUT...
1#- so a special planetary wepon will be needed, ok fine, but wep. equiping it no problem
but orbital artilery ? gee... i dunno about that (but its not an "NO" just sound strange)
2#-why not ? you can drop attacking forces on the pllanet then return on the map system & wait till resoults
because hegemony planetery defance force will be usless when they lost their planet in just 1 day
i prefer something like:
select planet *POP UP* window>select attacking force (soldiers,tanks,you name it or whatever, support orbital vessels) & after that you have to wait some time & camp/deffend yourown forces so hegemony(or any other attacking forces) dont send rainforces from the orbit