Hell, if you want even more energy, ask Suika to make a miniature black hole and collect it hawking radiation.
Doesn't seem very efficient though. You only get as much energy as you put into it.
I mean, these types of magic already violate most physics, but I'm pretty sure with most characters' abilities you could come up with some clever excuse to make it work in theory.
Still though, Iku could feed directly into the grid, bypassing pretty much all limitations.
At this point though, pretty much every character's abilities would be really useful if they weren't restricted by the plot. Like imagine an ordinary day:
Sakuya tries to knife Meiling for sleeping.
Hisoutensoku released.
Meiling is now a playable character, so she can graze!
nope.avi
Meanwhile...
Komachi gets her job done in 10 seconds by making the distance next to nothing and using her boat as a bridge.
Meanwhile...
Reimu resolving an incident as usual. And then she realized she could teleport so she teleported to the final boss.
Meanwhile...
Yuyuko realizes that not only can she fly, she also can't die! Yuyuko went to visit the moon.
Meanwhile...
Flandre's wings shouldn't be able to generate much lift, but screw physics. Also given that she's an EX boss how did Remi and the others manage to contain her for 495 years?
Meanwhile...
Someone actually beat Yukari?
Yukari flips border of win and loss.
Guess Yukari wins again.
Meanwhile...
Reisen can become invisible by inducing hallicinations. You saw nothing.
There's tons more situations we could name.