It's not offset if you have a mandatory sweeper
Offset would be able to put it away like sturms, but no matter what you will have less combat power than regular RE. Basic maths, 5 stens better than 4
minesweeper comes "free" without having to pay 30 munition.
The unit is slightly more expensive but it trade utility over firepower compared to R.E. so I am not sure what you are complaining about.
And not there is very little reason that they should be able to put away the sweeper, they unit is already dirty cheap and one of the most cost efficient engineer unit in the game.