The question is: What exactly is the reason that makes you looking for something "Mega"?
Since imho for music there is no "the bigger the better" as it might be a sellingpoint for popcorn, pizza or SUV's.
If Japanese enthousiats for instance perform every year Beethoven IX with thousands of participants it might be an extraordinairy expierience being part of such a large choir, but I fear the musical quality does not necessarily benefit from the amount of participants.
In general things become more and more 'blurred' and languid the larger the sectionsize is. So if you think about the overall tendency of Dietz suggestions they all tend to give the larger Setionsizes more presence and detail by adding smaller sections or soloists.
However I am sure you know if you would take 100 soloists samplesets you will definitly not become anything "Mega" in any way at all. since however adding different samplesets does not necessarily make the impression of something in anyway larger.
So my suggestion will be nearly the same just formulated as if it would be the opposite:
Do the music you intend with medium or smaller section sizes (Dimensionstrings or Chamberstrings) and ask your self if, and in which occasions you realy want and need more blur, more languid gravity and less clearness and precision to get what you want, add than as much larger kind of section size like Orchestral Strings, or Appasionata. as you need.
Thinking about Synchron-Strings I would also think that the way you mix the ambience might also help to strengthen the impression of a more or less large section.