There is no best mod out there. Though, if you liked Requiem, try out 7 Deadly Sins and Sins of a Galactic Empire for a different, but still entertaining, Star Wars-y experience.
The Death Star though is sadly a much bigger challenge, and both in trying to fit it in game and with balance.
There's one way I can think of getting a Death Star to work, gameplay wise. Make it an unbuildable Titan, and then build a map around one player having the Death Star and the opposing player(s) having some sort of advantage (bigger starting fleet, more planets, etc) to achieve a sort of balance.
Making it a regular, buildable, Titan or starbase wouldn't really work for Sins, due to it's scale and weaponry, it's superlaser isn't as much of a problem as those two.