A cool idea for your mod is to make it so that every time an year passes the lifespan of everyone increase by 5/10 years (so not actually skipping time and counting possible events, as it would take too much time), this would increase this game difficulty, and it would bring a bit of "realism" since most cultivators are supposed to die of old age before achieving immortality. This would also justify the stats increase, as many people didn't just double their strength in the span of a single year.
You may also make it so that this stat increase also influences lifespan in a far lower range, so at higher cultivation, most people would be the actually talented ones (a better way would be to have them have an increase of EXP so they reach higher cultivation realms faster).

Another idea is to set this grow up increase so that it is stronger in people with titles or with red destinies, and stronger in people with orange ones than in purple ones, etc. so people who the game tells you have better talent actually are stronger. In my save, this guy who could easily kill foundation realm cultivators while at qi gathering was supposed to have "weaker destinies".
To achieve the same effect you could alternatively change the destinies values so they give a huge flat increase, if this grow up increase influences stats values after they were modified by these destiny values, people with a +20 atk at the start will be able to remain stronger than most even in the end (this would also resolve the problem of many destinies being useless after the first hour of the game).

These are just some ideas, I'm not expecting you to spend time on these just cause I'm writing them, of course. Just saying that they fit the intent of your mod while addressing some problem in the main game.