I'm a fan of the
Plague Legion Remnant codex, it emphasises everything I like about the Death Guard while
de-emphasising the things I don't. That said I'd only ever use it for modelling inspiration, not as actual rules.
When I was in school I'd make a bunch of homebrew codices, for things like squats and rebel grots and other niche forces, nowadays I find them to be interesting intellectual exercises in rules writing but most people won't ever use them so there's not much point, I tend to write
RPG homebrew more these days.
Most homebrew either just takes
GW art and reuses it or forgoes it entirely