If you had a certain price on exchanges (let's say $0.50 USD per coin), and you wanted to increase the profitability of this coin, you'd have to increase the reward so that people could mine more with a given hashrate. This would mean that your coin's network would have to be producing more coins overall. Your miners (in the short-term) could then sell these coins for $0.50 each and make more money, but people would quickly wise-up and realize that the coins are not as rare as they were before, and the price on exchanges would plummet.

Sorry. Correct me if I'm wrong, but I don't think that this is a workable idea.