The Crimson Binome
Hero
That's not really my prerogative. When I volunteer to run a game, I'm signing up to deliver a certain experience. Even if I have house rules, there are certain core system mechanics that I'm not going to change, because they're too fundamental to what the game is. The rules for determining DC and making ability checks are of that variety. If I'm not willing to respect the core mechanical premise of the game, then I shouldn't be playing that game.Then don’t ask for a check.
As the DM, you don’t have to ask for a roll. You can easily say training is an automatic minimum success and give the option of rolling for even better results.
It's not like the entire system falls apart when you use the actual rules. It's still just some occasional weirdness, and every codified system is going to have some weirdness. Arbitrarily saying that a particular fighter can't even attempt a DC 12 check, because their bonus is only +1 instead of +3, feels like it's crossing a line into the realm of pure DM fiat.