I thought during live the limit was 5, but I guess not. I truly wish they would give us 10 arcs per account or even allow us to buy arc slots with AE tickets.
Finally joined the server after years, last month, Donated today, I hope it helped, I can't afford a lot, but I want to do something to thank you for keeping this game going. As I can, I'll give more.
Update, I went to James Frost in the Freedom Corp building in Atlas Park. he is the Respec Contact. Not only was I able to respec, but I also got all my lost enhancements back.