With the current state of the game, I don't miss many new girls from the mega events anymore, but I also have quite a backlog from before this year.
Hot Assembly by its nature will almost certainly put any girl you don't complete into Sultry Mysteries territory.
For Lusty Race I seem to be landing in the top-100 every mini-race so far, which means that a single gold investment gets me all the girls. (HH is harder due to more players)
Only the Seasonal Event takes extra effort to get the 3rd girl, with the 4th out of reach no matter what.
So that's only 1 or 2 girls every 3 months that need special attention for revival in the future.
For the seasonal/mega girls I need to catch up on, I keep some sapphires in the mega event markets to buy at least 10 (but probably 20) shards for each missed girl that shows up. Labyrinth in normal mode generates enough extra coins to push them up 40+.
And since I generate quite a bit of surplus gold, I can actually afford to buy extra keys to accelerate the coin generation in Sultry Mysteries. Admittedly it gets expensive if you need to buy 60 legendary shards that way (about what a mythic girl costs), but I've got nothing better to spend my extra gold on.
Agreed, I will miss that one too. It was high on entertainment (even including some actual written mini-stories) and not hard to complete once the epic nightclub pool is finished.