Yup, that's good idea
default rating for Chess960
I agree with you, but we could take it one step further. For example, I have run into sevrel people that have 1500-1600 live chess ratings, but have never played a online game. They usally win all the tournaments. My suggestion is to have their online rating 200 points below their average live chess rating.

Here's a perfect example: http://www.chess.com/echess/game?id=96957744
@palestine2014 (online chess: 1613) is going to slaughter @tommuhiid (online chess: 1215). It makes no sense whatsoever for them to be paired in this match. But that is how the algorithm currently ranks a player like @palestine2014 who has never played Chess960 before.
It's demoralizing for the team manager and it's demoralizing for the player who gets crushed.
I have seen a lot of Chess960 tournaments and matches and have the following suggestion. Currently, players who have never played a game of Chess960 get an initial rating of 1200 or "Unrated" (I believe I have seen both cases).
My suggestion would be to give those players an initial rating as follows:
Initial Chess960 Rating = Online Chess Rating - 150.
Example: Player A has an Online Chess rating of 1800 but he has never played Chess960 before. He now signs up for a Chess960 tournament or match. His initial rating would be 1650.
Why? Players are very commonly mismatched in Chess960 matches because they have never played Chess960 before. Even though it isn't perfect, I think this system would work better than the current system (in which everybody is 1200 to start).