Speaking as someone who builds speakers, I wouldn't say that removing the crossovers and sending them somewhere is very simple. Especially for those who have never opened up their speakers.
Jsadurni, I disagree that a better tweeter will be more efficient. It is completely driver dependent. Some are efficient, some are not. In addition to needing to potentially pad the tweeter (which is a good point) the crossover point could need to change. Which means complete crossover redesign on the tweeter side assuming it is a parallel crossover. If it is a series crossover, good luck. Some tweeters can cross low, some can not. You would have to know the optimal crossover point and find a driver that met those specifications. No simple task.
Jsadurni, I disagree that a better tweeter will be more efficient. It is completely driver dependent. Some are efficient, some are not. In addition to needing to potentially pad the tweeter (which is a good point) the crossover point could need to change. Which means complete crossover redesign on the tweeter side assuming it is a parallel crossover. If it is a series crossover, good luck. Some tweeters can cross low, some can not. You would have to know the optimal crossover point and find a driver that met those specifications. No simple task.