I would think "take home" implies you take it home, i.e. do it in your own time. I don't know what your undefined "other things" are.
> The 2.5 hours will also scale up with the number of participants, 20 employees who are committing 2.5 each week (at very, very minimum) is a loss of 50 hours per week.
It is this sort of thinking that is super counterproductive. Even if one of those employees learns something simple, like how to programmatically create CSV files and import them into Excel, they will have saved thousands of man-hours.
You can't nickel-and-dime people's time like this. Philosophies like yours tend to end up with timing people's bathroom breaks and scathing articles in the newspaper; rarely successful companies.