It really depends on how you want to play the game. Years ago we just got tonnage and picked a map, randomized where the maps we selected went, and had a game of what is basically now "team deathmatch".
The older scenario packs, I mean early 90s type such as McCarrons Armored Calvary, are more along the lines of what you might want. I cannot tell if you want to design your own forces, or if you want premade forces on predetermined maps. The MAC book starts with a few fights and if the attacking player is able to win X amount of those fights, the campaign goes onto the next phase. That phase then has Y amount of fights and if the attacker wins enough they can switch to a different line of battles, if not they go to another line of fights. If the attacker wins enough of each of the fights to progress to the branch with the "good ending" for the attackers then they win. If not, then the defender can win by forcing them to run the 'bad ending" scenarios.
As for a large scale planetary assault, that scale of the game is supposed to be in the Interstellar Ops book which is coming out "who knows when"tm which is supposed to cover everrrrrything. Some of the older, but newer scenario packs such as "Operation Stilleto" have a way of running your own forces instead of something someone else designed.