I have a 139 Mercedes at the moment, 87 Luminous, and 84 Kaiser. Is Merc any good late game, should I keep working on him or should I just pool my efforts into something else?

I'm not funded, so basically I guess I'm asking what the best unfunded class is to play to get money.

mercs are one of the strongest if you're funded.
If I were you I would stick with your merc. Use your kaiser/luminous to farm coins and fund your merc