Seems like there's an issue where if there are any creeps in the cells where the ramparts would be built, some of them don't get built. Seems like the rampart under the builder that lands the last "build" is built, but if he has helpers, the cells where the helpers are remain empty

You don't get the 3 days of protection after each respawn, it's a timer that starts the first time you spawn. After that, you get an hour or 2? At least, that's what I got last time

While storing the energy in the pile is kind of ok, I would much rather prefer the new structure type:
something like 'storage' which can store a lot of energy without losing it.

I actually had the same idea. If you made it able to transfer energy to spawns and links, it'd have some interesting uses as remote storage and such.