I've never brewed any Cooper's kit before, but:
1. You could swap DME for sugar pound for pound. Table sugar produces a little more gravity, but I wouldn't sweat that. You could also use some of both sugar and DME...sugar isn't bad in small doses.
2. If I were to add hops, I'd add them late. 15 minutes, 5, knockout....maybe dry hop. It depends on what you want.
3. This is a no boil kit? I think you could steep (or even mash) some grains in the water you use before mixing. All kinds of choices, but I'd keep the amount low if youre using Crystal.
4. I'm guessing that uses Cooper's ale yeast, which I personally kind of like. I have no idea how fresh the packet is.
You hav a ton of options on how to 'hack' this. How much money do you want to spend? My personal priorities would be (1) DME instead of sugar, (2a) some flavor/aroma hops late or (2b) try another dry yeast, such as S-04.
Here are some hacks: