Thinking over a quick and easy way to do conditions I decided that really there are three basic states for a creature: 1) fine (no impairments), 2) suffering a condition which partially impairs (such as blindness or nausea), and 3) suffering a condition which totally impairs (such as being paralyzed or unconscious). Fine is fine and totally impaired is totally impaired, so we really only have to tackle conditions which partially impair. I decided up front that there should be a single, easy-to-remember mechanic for all impairing conditions (as opposed to a massive list with finicky micro-rules). In the end I went with the advantage/disadvantage mechanic from D&D 5th Edition.
So when a character is suffering a condition which partially impairs and they need to roll for some action, the GM rolls a d12 against them which is the condition die. If the condition die beats the character's roll, either the 1d12 roll for an attribute check or the both of the d10s (individually) for an attack roll, then the character action fails.