What adjectives can you combine with drop-dead to emphasize?
There's drop-dead gorgeous, can you also combine others like "nice" and "simple"?
According to a contemporary English corpus, drop-dead is only used to intensify adjectives related to beauty: gorgeous, handsome, etc.
You can sometimes omit the intensified adjective.
Of course, there is also a more literal meaning of drop-dead.
There is a possible connection between beauty and simplicity, however, both of those combinations sound wrong to my ears.
"Drop dead" is an "extreme" adjective. So is "gorgeous." But "nice" and "simple" are not.
I would use an extreme adjective only in combination with other such adjectives.
And preferably not at all. Unless one wants to get a reputation as a "hyperbolic" (extreme) speaker.
If you modify an adverb with the phrase drop-dead, you're saying that it's extremely/intensely/incredibly [adjective] - so much so, it might kill you on the spot.
While someone might be gorgeous enough to invite heart palpitations, it's harder to imagine the effect of someone's kindness or simplicity could be the same.
Personally, I don't think there's much of a reason to expand this modifier's usage; it seems more likely you'll misfire and raise eyebrows than anything else.
If you are going to use it, use it with intense adjectives, keeping in mind that most speakers are used to hearing it only in a few stock phrases (and those are generally beauty-related).