Yes. There is a disadvantage, that when your app already exposes metrics, you will have to tell prometheus' service discovery that you want to scrape two ports.
Well, you can easily set up Prometheus with a rule that automatically scrapes any discovered service (or pod) where the port name is =~ /^(exporter|.*-exporter)$/, for example. This allows you to name your port just "exporter", or you can have multiple ports named things like "volume-exporter".