Separate Game Difficulty into Geoscape and Battlescape

[Forez]

The idea is to make it undefeatable, but so rare that it will not seriously impact the course of the game.

In alienMissions.rul there is
 - type: STR_ALIEN_RETALIATION
    points: 0
    objective: 4
    spawnUfo: STR_BATTLESHIP

Which I gather spawns a battleship to attack your discovered base.
   
UFO spawned is the BATTLESHIP which selects a battleship or one from a list of different interior styles if using a mod such as DARKENED UFO's.
   
 However all battleship maps alienDeplyments.rul have a certain number of aliens aboard and hitpoints, that is I do not know how one UFO type style  can be modded to have more aliens or hitpoints  than another style  of the same type without defining another ship type entirely.
 
 We do not want  all ALIEN RETALIATION missions spawning DREADNOUGHTs except rarely.
[...]

So how should this works in the big picture?

Such over the top ship would only attack base- but it still would had to fly to it, right? And what if it gets shoot down- you can loot it, right? Or you could just ignore such potentially extremely hard to claim wrecked ship, right? And if you defend the base, you get weapons and points, right?

So all in all just an another kind of ship / attack based on the already existing options could actually speed things things up instead of slowing the player down [aside from the the actual extra gameplay time]?


So it seems that only bad things coming out from the script, that cannot be averted and can only be repaired / restored afterwards would do the trick [like the destruction of some of the hangars even after successfully defending a base]. Or literally a insanely costly ticket to Mars- be it in money [millions spend on modification for the Cydonia flight] or in Elerium [thousands needed for the flight itself]

[SteamXCOM]

So how should this works in the big picture?

Such over the top ship would only attack base- but it still would had to fly to it, right? And what if it gets shoot down- you can loot it, right?

You cannot shoot the dreadnaught down and if your base is defended to the maximum inasmuch as facility defenses go the best you can do is drive it off.
The idea is to create something that, to battle against it, at best is a draw, at worst is a base loss.   It cannot be  something that will benefit the player as you describe but introduce a rare but exciting menace that kicks the player on the way to the finish line but not make the game unbeatable.