Optional "No Unit" Quests, Queued Mistakes

It's been discussed previously and unfortunately as far as i understand with how the game logic works, there's no easy way to write or build that distinction in, for what is essentially a really annoying inconvenience. I know i've brought this up before and it also drives me nuts. It's really easy to do when you're using hotkeys for unit training and accidently hit the key beside the correct one. There's one civ (babs or persia i think) that changes the spearman hotkey (as an example), and when you're running a "build only spearman" objective it's really easy for muscle memory to kick in and hit the wrong key (a split second mistake and you've only queued the unit, not trained it).

 

Persia, because Sparabara are the age 1 infantry

Don't worry, everyone that PvEs wants this. Problem is as t31os has mentioned it'd involve back end changes which limits the people that can work on it to the 4 busiest devs aside from the animators. Granted, considering how "build x unit type by y time" quest requirements work (by requiring the unit/s to actually finish training) I've always wondered if the code for that could be repurposed for "don't make x unit" quest requirements.

 

Wondering if there is another way to solve this.. Like may be pop up a confirmation dialog if you are trying to create a unit that is banned by optional (for the first time)?