First thing I did when I first got the game was start up a single player game as LA Ermor, so I know the feeling
That said, I don't think it's the best choice for your first MP game; I ended up as them in the first game I subbed into and I got steamrolled (though it had a lot to do with the position the nation was in already, to be fair.) Diplomacy will be very difficult, and it would probably drastically shorten the game either for you or everyone else. If you do decide to take on LA Ermor, though, make sure your Pretender is awake and good at Death magic, otherwise you won't be able to get your mages unless you get very lucky.