I think the easy way around this is to give up on people's feelings. Everyone will take a few lumps when they first start. If you happen to match up against a team way better than you, you're not an idiot. You will realize that you will get beaten badly. You deal with it and build your team.
If they choose to do so, a drop-down menu option will be sufficient. After all, there are times when you'd like to conserve the starters if you're winning the game.
I do agree that it will be beneficial in terms of controlling training minutes, and I remember suggesting a while ago that the blowout rule be altogether dropped from non-competitive games without any options.
"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve."