increasing his bounty would infact make him have the highest bouty - one the most wanted man in the world. Doubt they would d this since there is afuckton more people stronger than luffy as it is.
Would be understandable if they increased everyone else's bounty aswell tho ( eg. dofla)
But I don't think bounties are based on strength. I think it depends on the actions of the person. Dofla's bounty's just 340m since he became a shichibukai (which stopped his journey) and probably since he has no major problem with the WG. Just sayin'