Dealing with Variations to activitiy scope

Guys

Could really use your help on understanding how the industry deals with variation to an activity scope

For example if I have an activity with 100 manhours in it with a duration of 6 weeks - If I get a variation at week 2 for 30 man hours and 2 more weeks duration .......

I could add this directly to the activity - but this gives no real ability to track or report

I could creat a new activity - enhances reporting but could get messy if you are time writing at activity level (imagine if you have 50 variations)

How do you guys dealt with and track this in industry ?

Let me know

Neil