To me, as an aside means similar to "順帶一提"...
"I am writing to you to discuss the important changes we are making for the annual senior class trip to ABC park. Due to safety concerns, we need to restrict students from accessing the water ride, which caused two injuries last year. As an aside, the water ride has been traditionally the most popular ride among the students."
So in the sentence your focus is on "changes to be made", but just "as an aside", you want to bring in this other piece of information, that the ride has been popular.
Hope this helps.