Mostly it is different in that experience levels still exist and are used both to determine your max over all stat level, and whenever you gain a level you get a big random boost to your stat tallies. The actor class's stat growth curves also determines how much each stat level is worth.
Anyway the basic idea for how it works is stat tallies are used as percent chance that that stat will level up after battle, so if a stat is tallied 100 times it will always level up, but if it is tallied only 10 times you have a 10% chance. Tallies are remembered across battles but the level up chance only happens at a battle's conclusion. If a stat is leveled up a flat 100 is subtracted from the tally, and it can go into the negative. This practically means stat increases are random but predictable over a large period of time, and since your level acts as a cap for how many stat increases you can have and your class acts to show how many each are worth, the fact that the stats always grow at the same rate is not as important.
It's probably not going to be useful for most people's needs since it doesn't try to exactly match the system used in the old games, and is mostly me just experimenting with the mechanics. It might be useful as a base if anyone wants to do something similar though!
Here is the script: