Power by Max LCAs with ProKit springs
 

I'm looking at doing this combo along with the factory bolts to adjust front camber.

These lcas do lower the car an extra 25-40 mm depending on your choosing. Will this make the rear sit lower and look mismatched to the front? Are these necessary for prokit?

http://www.partsshopmax.com/page.php?14

Those are intended for coilovers, so you can get really low without losing as much travel. Alternately, you can raise the coilovers to keep a more moderate height and have even more travel.

With springs, it will just make the rear 25 or 40mm lower, with no way to match that in front.

I do highly recommend their products. Cool guys at the shop, and they don't make junk parts. I'm only running their spacers right now, but I will pick up the LCAs if I ever go coilovers. I've ridden in the shop FR-S and it is not harsh like I would have thought for a car that's nearly scraping the ground. It WAS noisy, though, with all kinds of solid bushings.

What solution is there to fix minor rear camber issues?

A different set of LCAs that use stock mounting points for the shock. I believe the Whiteline set is a reasonable price.