I’m not sure I agree without additional context. ICMP exfil is a known technique. Wouldn’t you want to know if all of a sudden, you started seeing gigs of ICMP? Or is there some other limitation that would make detecting this problematic?
What I would recommend instead is simply adding the protocols to the ports. So, instead of “top ports: 53, 80, 443, 8” you would see: “top ports: 53/udp, 80/tcp, 443/tcp, 8/icmp”
Would this be sufficient to solve the ICMP/port number confusion?