House rule: if a character wants to make a Perception or Insight) check during combat without using their action, allow them to roll at disadvantage. Thoughts?

Idea for a #dnd house rule: if a character wants to make a Wisdom (Perception or Insight) check during combat without using their action, allow them to roll at disadvantage. Thoughts?
I think it works for sure and would be happy to use it, though for me this is covered in passive Wisdom (Perception) scores. There are some SUPER edge cases where it would make a class feature (Eye for Detail) or monster abilities (dragon legendary action) SLIGHTLY less special.

— James Introcaso (@JamesIntrocaso) October 9, 2019

Mm, good point with those features, though the players don’t necessarily know what the monsters can and can’t do with their actions! I think using straight passive Wisdom (Perception) is too good for characters with high Perception, though.I think the assumption is passive Perception is always active (heh), so is the house rule also saying that isn’t the case? Or am I wrong? (Books not nearby.)

— James Introcaso (@JamesIntrocaso) October 9, 2019