Partial grille block is the only thing on you list I think is worth doing. If you want a 5sp and blower I've seen Ion Redlines with under 100,000 miles for under $3000, just get the whole car.
You will probably need front wheel bearing before long. You could upsize the tires when time to replace. My 2010 LT came with 195-60-15, I replaced with 65 so same size as my XFE, I think could even go to 205's for summer use.
Front speakers will fail if they haven't already been replaced.
If interested in Fuel system, you can convert them to FFV so you can utilized E85 when it's cheaper.
2007 Chevrolet Cobalt
Don't think yours would be as easy as mine, but if you can find the right tuner might be able to optimize for FE. Or buy HPtuners and do it yourself.