You could cut that tree at the base and it would likely sprout back just fine. In trimming, less is often more. Especially with a tree you see every day and want to look nice as it sits in your landscape. A tree's leaves are its income. If you reduce its income, the whole tree has to live on less. My suggestions aren't for a nursery using production methods to get the stock out as fast as possible with a good central leader, I'm talking about optimal health of a tree, and keeping it looking good. If it were a one and out type trim job, then yes, go heavy handed. I appreciate your point about species, it's basically a silver maple planted about 20 feet from his house, maybe he wants to slow that thing down.