Going over what I know. I feel Maple needs two skills and a realization.
First, the two skills. Maple needs an auto-regen skill, even if its just something like the Battle Healing that Kuromu has, and a skill that boosts Maple's HP based on the level of her VIT.
Second, the realization. Machine God + Destruction Growth is OP. Machine God sacrifices equipment to work, and the power of Machine God is dependent on the power/quality of the sacrificed gear. Her unique series gear, whenever it gets destroyed, skips the destruction animation, fixes itself, and becomes stronger afterwards. Together that means that she uses Machine God, which triggers Destruction Growth, meaning her gear is stronger after coming out of Machine God, and because her gear is stronger, the next Machine God will be stronger, continuing the loop.
By the time there's any "Final Boss" material, her basic armor's going to be able to tank whatever non-piercing attack said boss will throw around, and using Machine God could very well one shot the thing. (ah, nothing like overtraining so you can one shot final bosses...)
