The courts have historically been unlikely to see a Constitutionally-required affirmative permission in the fact that an additional restriction is not applied by Congress.

The fact that Congress has specifically granted permission under the Emoluments Clause to Presidents, at the latter's request, while the conflict statute was in effect wouldbsuggest stronglynthat neither past Presidents, nor, more importantly, the Congress has viewed the non-application of the conflict statute to the President as a grant of permission under the Emoluments Clause that makes more specific grants unnecessary.

OTOH, absent coverage under the conflict statute or some other statute establishing judicial remedies, there may an argument that there is no such remedy for a Presidential violation of the clause, and that the only remedy is via impeachment. That's probably the biggest weakness in an Emoluments Clause lawsuit.

On the gripping hand, a court ruling to the effect that the only remedy is by impeachment may create additional political pressure on Congress, which would probably have value to those bringing the claim, perhaps moreso than a judicial remedy that, e.g., forced Trump to give up past gains and avoid future gains through divestment.