My goal is to create the first Electrum server that allows this.
Too bad (a good thing actually now that there'll be 2), electrum.labrie.ca beat you to it.
But I'll continue now: Fulcrum is at 94%, speed is down to 1-2 blocks per second. So about 12 hours to go. So far, the database is 152 GB.You will need https://github.com/spesmilo/electrum/pull/10096 for the client to allow attempting the broadcast.
I was expecting a config setting to change this, but it looks like it's more work than that. I'll probably get to this tomorrow, once it's complete.