i appreciate everyone's input.
My question was in regards specifically to MX IKEv2 with a Fortigate firewall.
At its most basic config, the tunnel would not come up.
I did find that it is a compatible configuration, however there was a gotcha... Even though it was a direct connect to internet, on both sides, no NAT devices, absolutely nothing in the middle, it wasn't until after configuring the local and remote IDs, the tunnel came up.