Changes to fundamental game mechanics should not be done on some arbitrary basis to railroad the direction. If you want to stop the scramble for Africa from happening in the 16th century, design the game properly, and have it apply universally - if Euros aren't, Ottomans shouldn't either, not even Sahel empires, and same should apply to places like the NA interior and east Asia.
The BEST solution isn't to punish players for deviating from history, it's to encourage optimal play to follow what was historically an optimal route. Perhaps something rather simple - remove the distant overseas cost reductions for non-coastal provinces, and do not allow non-coastal trade company provinces, and shaft the value of distant overseas non-trade-company provinces. The NA interior will get colonized, because of CNs though. The African interior should go ignored while coastal TC provinces are still claimed. You even take a swing at distant overseas core creation abuse on the side.