This was announced a few months ago, it is now possible between 7 a.m. and 9 a.m. or between 8 p.m. and 10 p.m. for a group of 5 participants if you have €5000 to spend.
See here:
https://experiences.hhticket.gr/product/the-acropolis-experience/
I tried to buy a ticket, but the system crashed... :))
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