Maybe, but I don’t know that is a good assumption because that experiential happiness is, by definition, fleeting. That reflecting fulfilling memory lasts longer and I don’t that is maximized under that assumption
Altering a person's chemistry is exactly what a drug does, so I may be missing what you're trying to illuminate here.
"Could" there be a drug that makes people both experientially more happy and more industrious to the point where they have more reflecting happiness? Sure, but there could also be drugs that cure cancer and make us smarter at the same time too, I just don't have any pragmatic reason to believe we'll see one anytime soon because I suspect they work on very different mechanisms