This feels like it's only useful for warclaims and nothing else. Prolly gonna cause more harm than good outside of warfare if I had to guess.
Also, really? I have to ask mods to leave a realm? RP is fluid and characters inevitably bounce from location to location. Pretty sure my now-dead previous main character Jol went through at LEAST 5 different "realms" in the span of a year. I'm not a plugin creator, and I don't want to be an armchair dev, but is it really that hard to add a command or UI option to leave a realm?
If it's frequency of leaving that the mod team is concerned about, toss a cooldown on it, or only have it be a cooldown during war, idk.
As others have stated, inevitably certain folks who are obsessed with grinding out activity will target new players and rope them into a realm they're not really that interested in, and new players probably won't understand how realms work. Plus, if I understand correctly, this also means that you can view a persona's nationality at will as a player.
RIP spy RP because meta go brr
TL;DR a fine idea, flawed execution imo.