It might look like you sold it if you do, and you might get audited (Coinbase reports accounts with transactions above a certain level), it might be difficult to move it all at once, and you better be super comfortable with managing your on wallet (might want to get used to using them with a small amount before diving all in with it), but otherwise, probably not a bad idea.
Coinbase is probably at much less risk than these other companies, as they make money entirely off fees, not lending coins out, and have weathered more bear markets than any other exchange at this point (that I'm aware of at least), so they're probably the safest place to keep it if you're going to keep it not in your own wallet, but still, not your keys, not your bitcoin, and all that.