I've not got details any more, I must have deleted them as a quick search of my laptop turned up nothing, but here's an overview of something I used in a 1e game set in the Outer Veil.
At the time of chargen, players rolled stats as normal but also rolled a "potential" for their physical stats. I had a small chart that allowed the potential to be between 0 and 3 higher than the rolled stat. It was weighted so most had the same potential as the rolled stat, looked something like this:
7- 0
8,9 +1
10, 11 +2
12 +3
+3 is a bit high, but it's easy to rework the table.
In game I used a version of skill improvement to allow a player to improve the stat towards it's potential. Put the time in and make a roll...
I used a potential in order to set a limit on how high a stat could go. Strength and endurance seem good candidates for improvement, I'm not so sure about dexterity. I prefer the idea of external mods - things like nanochines and chemicals to affect intelligence and education (I interpret education as a person's memory and ability to store and recall information, not necessarily a measure of their academic achievement) . I am pretty sure that there are rules in one of the 1e extra rule books for improving SOC, the gist if I recall correctly, is you need to hang out with people above your SOC and spend more money on your cost of living. Yeah, just checked Book 8, Dilettante, it has rules for upping your social.
Sorry I don't have more details for you, hopefully you get the idea and it'll help.