I would like the president to issue an executive order to have Marijuana removed from schedule 1 and then added to schedule 3 of the controlled substances act.
This will make it legal for any Medical professional that can prescribe medications to prescribe marijuana based completely on their medical opinion of what medicine is best for their patient. This change would not impact the state level unless that state decided to make the same change to their controlled substances list.
What this boils down to is legalizing medical marijuana at the federal level so states can decide for themselves.
Further it greatly reduces the federal penalty for the possession of marijuana as it would fall under the rules of schedule 3 substances