Well, there is certainly merit in what you are saying brother. However I think the example of the rich young ruler exemplifies those that were NEVER saved to begin with. (Although in his case we don't know if he repented and accepted Jesus).
This is always the distinction we struggle with. I can't find a single person in Scripture that ACCEPTED Jesus, and then either forsook their faith, or God cast them away.
Now there are GROUPS of people Scripture refers to, but I believe if we dig deep enough it always turns out that this passage applies:
1 John 2:19New King James Version (NKJV)
19 They went out from us, but they were not of us; for if they had been of us, they would have continued with us; but they went out that they might be made manifest, that NONE of them WERE of us.
On differences like eternal assurance, although I do think it can be very damaging to believe in a saved person losing salvation, (a true oxymoron right there lol!) I look to see if that individual believes Jesus rose from the Grave, and has confessed Him as Lord, and trust THAT Jesus HAS INDEED permanently saved them through THAT Gospel.
Peace, Grace, and Love to you! I hope you don't hold my faith in eternal security through Jesus against me brother.