Well it would be nice to have a merge command so hopefully you'll eventually figure out how you'd like to expand on your UI...

I'd think just add a "shelf" like you have for line and curve command options, however I noticed that you have a shelf for the curves and construct commands but nothing for the edit commands - they're all single function like you've mentioned.

Obviously this is your decision to make and we'll have to wait for you to decide how your UI is going to handle additional functionality such as this...

-Will