Reason 1: people won't be able to literally SPY on you by hugging a corner of a wall
Reason 2: If the player base is built off of 3rd person players and the server is switched to 1st person a couple months into it, this would be a huge gamble in itself since the people who play in 3rd person would probably want it to stay that way.
Idea 2: separate server for 1st person
(sure this would split the player base but hear me out)
You could use this idea as a testing period per say, see which server gains more traction and if they both get a healthy amount of players then good, if one gets a significantly higher amount than the other (30-40 player difference), consider mainly focusing on the more populated server, at this point i'm assuming the players from the other server would have possible made an account on the forums so they would know the reason why the less popular server was closed down and they'd (hopefully) just move onto the other OB hosted server instead of moving onto a different server with similar settings (aka if they get on teamspeak don't be a cuck and drive them away).