The trouble with using elliptical orbits to get low and close is that you're going incredibly fast at that altitude. This spells trouble both because you spend a small fraction of your time above your target, and because drag is proportional to the square of velocity, mitigating any savings there.

We do have uses for highly elliptical orbits, but they're usually used for long residency times on their high side. The Molniya orbit is a prototypical example.

https://en.wikipedia.org/wiki/Molniya_orbit

Tracking is not difficult for groups of amateurs with telescopes. Considering that you are up against large foreign states with extensive radar and optical detection facilities, it is mostly a lost cause. Satellites have enormous solar panels.

Elliptical orbits still require station keeping. Elliptical orbits tend to circularize over time from the drag they experience at the closest point to the Earth.