Matchmaking really isn't the way to go for Arena.
Problems with matchmaking are always a problem because they are never definite. Especially in this type of game. How do you balance how to Rank a ship? Averaging the players MMR in the crew??
Ive played games like Dota 2 and other games that used a matchmaking system. Its really not as fair as you think it is.
You think you'll be placed with individuals at your level but you really aren't. Unless the players you are playing with are exactly at your level you aren't going to get fair match ups. Then on instances where the game is deciding to raise your rank you'll be placed either against a fair match or more then likely against a team that is significantly better than you in every way because it was a rank increase match.
Then there are issues with smurfing which will be the new whine and cry about issue. Trust me its good as it is, it forces players to adapt or learn.
I hope they never actually do matchmaking/mmr/rankings but since they want to turn this into a Esports, I'm sadly under the impression they will ultimately do this.