What about making the Chinook land on/in a launch-platform/hangar bay for the ship's escort/alien landing craft. Bear with me for this. Have the mission take inspiration from BF2142's titans or Starwars battlefront's spaceship battles.
Lore Justification
The alien ships are enormous but even the cruisers are better in the air than touching down and trying to take off again. Kind of like an aircraft carrier or a battleship. They dock to repair and rearm but for the most part they stay at sea, using landing craft, aircraft etc to physically assault the position. They already have had to be refitted to deal with earth's atmosphere so it makes sense that it isn't ideal for the larger ships to touch down on ground where they are potentially more vulnerable.
"Landed" craft would then be hovering in place district 9 style (with engines on idle), or they have good reason to land (like to remove a funding nation)
When one of these is shot down, the easiest way to access it is to land the Chinook on the actual ship itself and to gain entry by either
a)breaching through a launch pad/hangar entrance or
b)through tears in the hull acquired during the air battle
Defensive weapons that could potentially damage the Chinook are destroyed/disabled during the crash, destroyed during the air battle or targeted by the squadron afterwards to prepare for landing, or their fire arcs are simply circumnavigated by the Chinook on approach.
What this allows
-We can still breach the ufo without needing a 2 part mission. Depending on feasibility, you could still even have additional breach options through damage from the air-battle or damage from the crash. (the ufo hit nose first and the impact stresses tore holes in the hull. Or maybe it broke open titanic style over a mountain ridge). This can allow for aliens to begin on the surface of the ship, coming out to meet you, followed by your breaching through the chokepoint doorway (airlock).
-you can see the whole ship on the map. it is the map. the pretty art can be seen in the tactical view even if you cant walk over the whole thing
-the maps can give the feel of an enormous ship but still keep maps within a reasonable play size by saying that you are landing near to the important systems, avoiding the problems with scale breaches. Imagine fighting up through the crew quarters (hundreds of xenos) of an actual battleship with a squad of 10 guys. A suicide mission at best.
However, if you land and breach near to the important systems, you could theoretically seal doors off from the rest of the ship, cut off life support, contain the aliens well enough to harvest what you want/can from the ship before detonating the remainder.
Problems
-Randomization would be interesting to work around. You could potentially randomize the ship interiors but that doesnt really fit mass production, oh well.
-claustraphobia. too much indoor gameplay, especially as you take these ships down more often later on in the game. environments get stale. no idea how to deal with this. Maybe in some ships your breaching path passes through a mockup of earth for practice encounters. houses and fields on the inside of the ship...
Well food for thought. Oh, and first post:)
