It’s being brought up in Warfleet the using the electromagnetic hold on the pelican while enter atmospheres are highly discouraged(never assume “high discouraged” actions to function). So does how could they bring warthogs and scorpions from space other than bringing the entire ship into the atmosphere?
Mongooses can be deployed using standard drop pods,so Gungooses can this most likely too.
Larger vehicles can maybe deployed using parachutes similar to the one drop pods use,only larger.
Larger dropships like the Albertross or Condor, heavy drop pods, parafoil, shuttle craft. There are other ways
Well from what we have seen in game and in lore, some UNSC ships actually can enter atmosphere. Also keep in mind that any dedicated troopship will have more than just pelicans to transport forces. Look at the SOF it has large dropships that help to deploy forward base positions and can presumably carry heavy armor with it.
If I remember right there’s like, air deployment systems that let a vehicle get dropped from above. We see em as the spawn points on Vahalla in Halo 3.
And of course, various dropships, etc.