It would be nice to have more control over network with GrapheneOS. At the moment GrapheneOS allows disable network on per-app basis, but I think some general network functions could improve security. Examples:

Enforce network isolation (Layer 3) over WiFi / mobile data
Disable multicast (Layer 3) over WiFi / mobile data (can be done via plethora of methods - from disabling multicast IP ranges to using "ip link" or "ifconfig" tools)
Disable ICMP (at least inbound echo types)
Disable all forwarding (can be done via SysCTL configuraiton)

VPN Apps already do some of that, but Android OS can enable mentioned features on its own.

BTW, is there a seciton specifically for feature requests? Is it better to post such requests GOS GitHub or here? There should be a forum section (and/or tag) just for that.