It felt like a missed opportunity to me from the beginning that super-weapons didn't cost power from the beginning. I thought it would be a great mechanic - for both the attacker and the defender.
And actually use energy: like 50 E/s continuously for 6 seconds after each shot, and if you stop firing, it just loads the next shot and now you have an extra 50 E/s in the bank. Also, naturally you'd discount bertha's price by the equivalent cost in power plants. It would look cool, feel cool, be fun to set up the grid, and be fun to disable it. Also, this would give me a reason to use fusion/geo.
Regarding Bertha, I absolutely adore the weapon. I love big arcing projectiles. To me, it's more enjoyable to use than every other superweapon. It might be the physics that makes it feel real.
However in terms of power, I was unimpressed with it. The extreme shallow angle at which it fires gives it irritatingly awful inaccuracy along the radial axis, even when I terraform it 300 elmo high. And the splash was disappointing too. I would like to increase the splash by maybe 10% or the accuracy by raising its angle of fire. (if it's at 15 degrees, I'd like to test 30 degrees, even if that means enemies have to build their defensive terra a bit higher).
If people think that would make it too strong, I'm highly in favor of nerfing its reload speed to make it a far punchier and more impressive shot. I'd be ecstatic if it had a 30-second reload (with buffed accuracy and splash to compensate) with a "bertha shot ready" tone when it recharged. And consequently most shots would be manually fired, and you'd want to watch them like you do a nuke.