It's not a matter of timing down the lower ranks. It's a matter of an overall decrease of credits per hour, as lower ranks also have lower bounty rewards, meaning that if you effectively eliminate targets with 50,000 CR+ bounties as viable targets for those working their way up, you've also decreased earning potential in a game where upgrades are already very slow to earn.
One of the major complaints currently is boredom. By increasing the numbers of NPCs that must be "farmed" in order to move into the next ship upgrade, you're also increasing that boredom.
This doesn't mean AI upgrades shouldn't happen. I would just suggest that bounty reward levels be increased to match the new difficulty curve. If an Elite Anaconda is now a 50/50 toss up for a player in a similar ship, the reward should also be increased to be closer to the insurance rebuy of the ship.