In the original game, characteristics were rolled on 1d100, and gained bonuses based on the number rolled. So, if the roll were 01-25, you'd add 25 points, making the stat 26-50. This is a little bit complicated, and it results in situations where a roll that was higher results in a stat that is lower (for instance, a 25 becomes 50, while a roll of 26 becomes 41). That annoys some players, even though I don't personally care.
The average roll using the basic Top Secret method comes out to 62.73, with a minimum roll of 26 and a maximum of 100. After experience additions, stats have no theoretical limit, though there are some practical limitations.
I'm thinking that I will include both that method and a simpler method. Instead of rolling 1d100 straight, roll 2d10 and choose the larger die as the tens digit, the smaller die as the ones digit. This results in an average roll of 65.45 with a minimum roll of 10 and a maximum of 100. Perhaps I will include the option of allowing the player to choose which method he prefers.
I'm definitely going to incorporate all of the various secondary and tertiary traits from supplementary material, which basically means that it will include the three traits from the Top Secret Companion and the two traits from "Operation: Zenith", Rasmussen's article from Dragon 120 that introduced the space program as an arena for espionage roleplaying. In addition, there are a few sections in some alternate rules that I plan to incorporate where averages of various attributes are used without declaring a new secondary or tertiary trait. I think that I'll designate some new traits to cover those.