@Dynamiez If you don't mind mods and are allowed to use them on your server, I have seen a mod called "PlanBuild" on Nexusmod.com. Originally, a mod, "Buildshare", was used but it hasn't been updated in almost a year. Players are posting their blueprints on the Nexusmod site for people to download as well. Personally, I have not used the mod so I can't say how stable it is.
PlanBuild:
https://www.nexusmods.com/valheim/mods/1125

Edit: I apologize I didn't read all of your post and see you already know about it.