How about this lineup?

Tanky tree, repetitive mysteries, mirror , healing , shields and 3 immune ninjas from the beginning plus removal of shields/buffs through the combo.

Also, if I use both Christmas Karin and Christmas Sakura in the same team, would there be two trees in battle? Would these two trees work for each other's passives? and would their effects stack? if yes, then maybe one could even try the lower lineup(or use water main with poison tai because both strong and normal poison stack each other as 4 separate layers, I just thought that ignition may be better)-

That's why the mirror! ;)

And please confirm if Christmas Karin and sakura's trees can substitute each other.(ie if sakura's tree is dead but karin's exists, then would karin's tree allow sakura to use it as her own and vice versa?).

Also, would the reduction in defense and resistance by karin and sakura stack?