No, really a NO.
BUT you can easy made a seletion ON/OFF for not so strong PC's.
So we can decide if the Frame drop is too much or not for our system.
You are confusing the two issues, which are entirely separate.
1) The lack of a 64 bit sim CANNOT solved by the most powerful PC in the world right now. a crowd of visible passenger WILL NOT fit in memory. We are ALREADY in the situation that with a memory-hungry airplane is very difficult to complete a flight on a complex scenery, there's simply no space left for anything more.
2) IF and AFTER we'll eventually get a 64 bit sim, we'll have to tackle the FPS issue so yes, in THIS case, it would be trivial to have an option not use visible passengers but of course, if the fps would be too low for even "the most powerful PC in the world", it wouldn't make ANY sense for us to work on a very complex feature that everybody WILL have to turn it off anyway.