From one who has not played AD&D since (checks) 1983 or so (and is ignorant of anything TTRPG since they stuck "1st edition" on its name) ...
Posit a D&D campaign being run in the Laundry Universe, during/after CASE NIGHTMARE GREEN (so circa 2015-20, in a world where magic has been out of the closet and rattling its fingerbones under everyones' nose since 2014).
What strange character classes and odd tropes might a sufficiently creative GM come up with? What existing mechanisms and monsters would have gone abruptly out of fashion, and what might be the new hotness in a campaign where some of the players might be accountants by day, and others might be capable of setting their hair on fire?
(Yes this is a "do my homework" question, and I have zero intention of explaining why. Suck it up!)