It would be very helpful if JMC could open the GC log files and present a graphical representation of the GC log files.

There is an existing GC log visualization tool - GCHisto:
https://java.net/projects/gchisto

There is no active development on this tool. It should be looked at if we can revive this tool and tie it into JMC.

There is a GCLog Plotting tool developed and maintained by JVM performance group:
https://wiki.se.oracle.com/display/JPG/GCLog+Plotting+Tool+V3

It is worth looking if this tool can be integrated with JMC.