The single most useful (and fair) thing they could do in regards to capital gains..
would be to index them to inflation. For example, suppose someone bought an asset for $10,000 in 1980 and sold it for $20,000 today. Sounds like he made a $10,000 profit, doesn't it. Sorry, but had the investment merely kept pace with inflation, it would've been worth $21,900. Instead of making a real $10,000 profit, he had a real $1,900 loss. The way it stand now, he'd owe $2,000 in long term capital gains tax, a raw deal and hardly fair.
The Inflation Calculator on the US Department of Labor website is a very handy tool.