There needs to be an upgraded version of the LESU for storing insane amounts of EU rather than some magic block that can store that much.
Seeing as you love 4-lettered Acronyms for energy storage, Greg, why not a similar setup like an LESU, but as a form of SMES (Superconducting Magnetic Energy Storage.) because right now, the LESU is cool in theory. But the input/output limitations make it fairly useless for the space and resources it consumes to give it decent output.
Capable of storing 250,000,000 EU with the base block and an additional 100,000,000 per attached Magnetic Coil block. With 512EU/t as the default output/max input that's increased by 64 EU/t per coil.
The SMES Block itself should/could consist of 2 Magnetic Coils, 1 Vacuum Freezer, 1 Highly Advanced Machine Block, 1 LESU Block, 1 HV Transformer and whatever else you can think of.
This has been suggested in some way many times, but this is definetly the best implementation idea I have yet seen. I completly agree, the LESU is awesome, but useless XD