The C-HR Hybrid isn't available in the US, where most of us are, unfortunately.
I would be hesitant to remove the spoiler; it's almost certainly there to reduce drag and rear lift. Most of it is slotted:
...probably to duct air over the rear window where it would otherwise have detached.
16" wheels are probably a good choice, especially if the wheels and/or tires are lighter--the 16" aren't even available in America.
It's probably already got iridium spark plugs (not an ecomod anyway, unless you consider longer spark plug life).
Does the C-HR Hybrid have the automatic grill shutters found on the Prius? If not, you can probably block some of the grill area.