Having said that, the default system is also ignorant to the current weigh of the elevator so it is still subject to stopping on floors without there being any space left.
Trying to figure out space available from the number of people seems unreliable, but I wonder if you can use a set of heuristics such as having a max weight at which point the elevator is assumed full and if it stops to let someone on but the weight doesn't increase assume the elevator is full (maybe require this to happen twice in a row?, IDK, false positives probably aren't too expensive.)