It is possible to configure network drivers at network create time:

docker network create -d overlay -o "com.docker.network.mtu=9001" foobar

In some cases, you need to change an option for all networks created on a system. Right now, the way to accomplish that will be to change every compose file, Makefile, bash script, or other deploy mechanism to accommodate this host-wide requirement. This is not a scalable solution.

There should be a ui/ux that would allow a user to set defaults system-wide: "all overlay networks will need to have this value for that option".

Implementing an alternate driver that has the needed behavior is not a viable workaround. It requires the same amount of effort to change all compose/make/bash/deploy scripts to use the alternate driver, so this won't address the issue.