As of today we do not offer any solution to merge two account, or to link an existing account to a Google Id.
However the 2nd point is a pretty good idea that we will definitely consider.
Just thought I'd mention, it appears I can connect to my original account - using "Sign On with Google" on the website - however it doesn't work when trying on the iPhone (where it sends me to create a new account (which.. already exists).
So I'm not sure if this is really a feature, or just a bug that needs to be looked at.
Hope that helps