To date, Nico destroyed Marcone's building, possibly killed some of his people, kidnapped and tortured and humiliated him, violated his accorded territory and authority, broke into his Accord-licensed bank, and killed at least one employee on that occasion.
To date, Marcone helped manipulate Nico into an action that cost him his daughter and closest ally.
I don't see either of them wanting to team up.
It seems more likely to me that Marcone will not work with any other Denarians because he will not trust them, and he doesn't need them, other than for muscle.
Even if he got coins to give to people, he wouldn't trust the people after they've got their own demon on board. Having the will to defy the demon has got to be rare, and not worth risking.