I recommend not using Coinbase in any regard and use another means of conducting your business with bitcoin. I can see this becoming a BIG mess. I now have to make sure I'm DEFINITELY organized. I can see a visit from the tax man very easily this year. If that happens, I will be on a mission to put an end to anyone doing business with Coinbase.
I doubt this is Coinbase's fault. They are a financial institution and there are very strict Federal regulations they have to adhere to. When you make a large deposit to your checking or savings the Bank will report it too. The transaction limit just smells like a government bureaucrat that probably can't even spell Bitcoin.
But please keep us apprised of the situation I would like to know what our liabilities are here in the US. Thanks.