Maybe someone can make a suggestion?
Remove the second level of alien base attack (no more nextStage: STR_ALIEN_COLONY_P2).
This would lead to:
a) Beginners can win against a base, eliminating it, reducing spawn missions and making game playable.
b) Experts get less synoniums and commanders, making the game harder for them.
c) Less bug using: Players could use the design bug to attack the same base again and again without completing second level, thus collecting huge amounts of valuable loot (early in game), while the base restores immediately after attack. I you want to completely erase bug using in this case, additionally add objectiveFailed: [STR_MISSION_FAILED, -1500] to the missions first level, so even looting the first level without completing is of no use any more.
The points b and c should be fine for meridian...