Making it harder to earn money wouldn't address difficulty curve issues much - it'd just make the opening game a little harder.
Well, making money should become harder as the laws move towards L+. This mechanism is already somewhat implemented in the game - selling brownies and art/music/donations become less profitable.
The opening game wouldn't necessarily become harder. At the beginning of the game, there should be plenty of ways to make money, but you'll have to pick carefully since your skills are still low. Later in the game, you have better skills, but you will need them in order to still turn a profit.
The main issue really is that, with the sole exception of Gun Control, every issue turning more L either makes the game easier for you or doesn't make much of a difference.
Well, womens rights makes a difference, depending on whether your Liberal is male or female. The percentage of female NPCs changes with the womens rights - at C+ you won't find female police officers/scientists/hangin' judges/etc.
If the LCS' hideouts were occasionally targetted by gangs and other criminals (to steal stuff or eliminate competition in the brownie business), liberal police and gun laws might also make the game harder - at C+, you'll have a fast police response and you'll be allowed to shoot the attackers (castle doctrine & guns are legal), while at L+ the police response will be slow and ineffective, and
don't you dare shoot the attackers since you'll have a duty to flee and guns are illegal anyway.
Also, with C+ gay rights it could be possible to blackmail anyone you seduced successfully (though attempting to seduce someone of the same sex should be illegal). As the law becomes more liberal, this option disappears.
At L+ animal rights laws, attacking animals (even guard dogs) should be a crime.
At L+ privacy laws, secrets (files, memos, etc) should be harder to obtain..