But one advantage to taking the Libertarian party line is that they have ballot access in the most states, meaning less work for his campaign. If Paul ran as an Independent or Constitution, he'd have to struggle a bit more.
In 2004 Nader ran as an Independent, but he still sought the Green Party nomination which would have given him ballot access on all of their states. Paul could possibly run as an Independent, and still seek LP and CP ballot access.
However, I think Rand is going to run in 2016 or 2020 and I agree this would hurt Rand if Ron ran outside of the Republican Party.