If the speed limit on highways was still in effect, but there was no punishment for speeding on the highways, then what do you think more people would do? They will ignore the speed limit and drive as fast as they like or feel seeing only the speed limit as suggestive. The accident, and death rate on highways would increase because people would be driving more recklessly (if such were the case, though).
Now, suppose a person had a license to murder, cheat, sleep around, hurt others, etc.; It would speak badly of the character of God in regards to fair justice in that a believer would not be punished in the final end for being evil, and it would encourage others to do evil in God's name, and it would lead many to treat sin not as seriously because God would not treat it as seriously. I see Jesus warning us in how sin can destroy our souls in Matthew 5:28-30, Matthew 6:15, Matthew 12:37, Matthew 25:32-46, Luke 9:62, and how loving God and loving our neighbor is a part of inheriting eternal life (Luke 10:25-28). Even the apostle Paul says be not deceived, the unrighteous will not inherit the kingdom of God (1 Corinthians 6:9-10).
So no. I don't see Eternal Security (Once Saved Always Saved), and the Non-OSAS Sin and Still Be Saved (Free Will Baptist) belief as being biblical, or good. God's grace is not a license for immorality (Jude 1:4) or even as a safety net to sin the rest of this life. Grace is there to help to battle and fight against mortal sin so as to overcome it (See: 2 Corinthians 7:1, Galatians 5:24, 1 Peter 4:1-2). If not, then one is simply justifyin sin and or evil in God's name. One has given in to their old man when they should have put on the new man in Christ.