There is no way even a top notch hacker or technomancer would be able to keep pace with entire teams of programmers who are working with mega-corp resources... Which in turn, means you would never be able to program a "Pilot" program past, maybe 3 in rating... (and that is pushing it)
And that right there ends all hacking in Shadowrun, flat out.
If that bit of reality is applied to the game, then Hack on the Fly and Brute Force actions are impossible in any timeframe because a "top notch" hacker or technomancer can't keep up with the ever changing security program code of a corporate host.
You know the code is constantly changing, if it weren't you would have at least a small window where you could use the exact same method you used previously rather than have to roll all over again.
On the other hand... If you are hand waving the reality of the hacker hacking, you can hand wave the reality of the hacker coding...