I used to do this, precisely because I feared losing my Facebook contacts. Messenger is very efficient & light, but once I realized how much I used other (although heavier) mssg apps instead, I saw no need for anything else. Mssg app for international family and friends, SMS for local, LinkedIn, Slack, Skype for work.

There are so many app alternatives out there (that are as well built technically) that you don’t need to rely on anything from Facebook's ecosystem anymore. Give it a try, no disappointments