A good idea for surviving on impossible could be the extensive usage of sacrifice to get back all your heavy losses instead of actually buying them back which makes you lose money and precious limited stacks of valuable creatures (e.g. royal snakes). All you have to do is to leave some weak mob alive as a controlled environment to do your thing and either hypno-sacrifice the enemy or buy cheap ass infinite "horde" critters and regularly sacrifice the crap out of them to either replenish losses or actually create full stacks of otherwise unavailable creatures. Like creating a full stack of horsemen early in the game as soon as you get sacrifice by luring out the huge mob guarding them through the pathfinding bug and making a full stack out of the mere 6 horsemen in the tent later. Also through sacrifice it is almost impossible to actually "dry out" a certain valuable creature's stacks
again like the royal snakes. As long as you got at least one remaining specimen alive and kicking, they're saved from extinction!
Maybe one could more easily tolerate the aftermath of critical battles with extreme casualties on impossible with the miracle of sacrifice!!! Sacrifice... don't leave home without it! Especially if leaving the home under an impossible difficulty setting.