You will need adjustable arms anyhow in the future if you're going to lower the vehicle. If you're planning to keep the car for 100k+miles, why not replace all arms at once? Just get adj. upper arm, and replacement for lowers too.
Your last statement doesn't make sense to me... You want to lower the car knowing the car will have negative camber => inner tire wear => new tire + adj. control arms, but doesn't want to change them because you are concerned about the stock control arm failure... ???????