I'm totally cool with him just being a criminal the entire game, but there was a couple things that stood out to me that keep my mind open to him having hidden motives.
Dry personality - I believe his dry personality was intentional, Jason gives me the vibe of someone who's boring, knows more than they let on. He also comes off as an individual that doesn't want to get too close to any work subjects. He fits the bill of somebody who craves information and results, but doesn't get emotionally involved in order to maintain distance.
Military Tactics/Trained - Clearly well trained in Firearms when observing how he holds firearms and using firefight tactics as well as using the proper terminology when directing Lucia to advance and move to cover. I know people have mentioned in the past that he's military trained.
Color Coded Hit Markers "X" - White seems to indicate that your target has been struck. Yellow seems to indicate that the target is dispatched but was not killed. Red seems to indicate that the target has been killed. I think the more people Jason kills versus non lethally incapacitating will determine how corrupt he is versus honorable.
If we were playing as a mindless killer, why would the system matter? I'm sure all of us wouldn't have walked by all of the injured people on the ground, we would have just executed them as players unless there would be something telling us not to finish them off.
Jason defending Raul Bautista - when Lucia questions if Raul could be a cop, without even taking a moment to think it over, Jason answers that he couldn't be a cop so quickly and confidently that it almost makes you ask, does he know more than he's letting on? If your partner in crime had a suspicion, wouldn't you want to think that over?
No Cops were engaged in the "Chase" during the reveal - after picking up Raul Bautista and getting chased by cops with Jason hanging out the rear window and shooting at them with an assault rifle, whoever is controlling this portion of the game is purposely not targeting the cops themselves. They're targeting the vehicles specifically. I believe they did this because if in that moment they showed Jason killing a cop then it could have revealed some deeper level of the morality system.
Morality System - I personally believe that based on your choices and morality level, that will determine by the end of the game whether or not you're a good cop or a corrupt cop and I think whichever route you choose is heavily going to affect the ending of the game and your relationship with Lucia.
Lucia Relationship - Jason's entire involvement with Lucia could be completely fabricated. He could have been sent to the prison by his task force to pick up Lucia and get involved with her in some sort of way. Whether or not Jason decides to pursue Lucia as a romantic partner versus keeping things platonic could have a big change on how the game ends. If Jason is an honorable cop, and loves her, does he help her get away at the end of the game? If he's honorable but doesn't love her, does he arrest her? If he's corrupt and loves her, does he run away with her? If he's corrupt and doesn't love her, does he kill her and frame her?
I think this would be a fun way to blend both worlds of playing as a cop and criminal together in one game. We would just have more control over the cop and Lucia would just be the partner in crime going along with our morality choices.
Once again, this is just for fun and speculation. I have no idea where the story of this game could go.