Once the NBA and the NBAPA figure out how to end the one and done situation, and let players go to the NBA (or else where) right out of college, then the NCAA will have figure out how to manage eligibility for rules for guys who want to explore the NBA option directly after HS.
If a kid declares for the NBA draft after HS, then gets evaluated and is told by NBA people to go to school, you're not even ready for G-League, what dates for determinations and declarations need to be in place? This is probably most important for kids in the ~30 - 100 range or so. Dates and timing for evaluation periods, declaring and withdrawing from the NBA process to go to college will be important. Will the dates be player friendly or coach/team friendly.
Kids could find themselves with reduced scholarship opportunities, as coaches fill their slots or coaches could end up with holes in their rosters if they hold schollies for kids who never show up on campus.
The top ranked HS players who want to go pro should be out of the college recruiting pool as early as practical. If you are eighteen, out of HS, want to play pro ball and the NBA/G-League is willing to pay you, go and best of luck to you. You won't be using a basketball scholarship to pay for college.
One thing that the NBA could do for those players it identifies under one of the proposed new systems is an NBA funded scholarship program. If you accept the NBA early entry, as part of the package you get a scholarship to attend college later, assuming your NBA earnings don't reach a certain level. (probably in the millions) You couldn't play basketball for the college team subject to NCAA rules, but would be able to get your education paid for. (Lookout intramural teams!)