I think pausing the campaign and putting them into a program that its goal is to assist the sales to close the deal is the best approach. What was your thinking begin putting them into an empty stream?
I would love to see how others are handling this.
2 things, from my perspective.
First, you pause the lead (#1). You do this because what if you lose the opp or recycle the lead/contact? Then you can un-pause and continue to nurture .. or they stay paused forever and you leave them as-is so you don't lose your reporting.
Secondly, you'll likely want to track the success outside of the EP as well. For instance, I have an sfdc campaign that I want to make sure I add them to to track my success, so that's a second smart campaign (the first being the 'pause') that I keep running.
As reference - this was how my Marketo Customer Success rep set us up when we launched Marketo last year -- I took it as best practice at the time, and have continued the concept throughout the rest of my nurture campaigns.
Hope that helps,
Please see slideshare.net/jdavidhill for details. This will answer your questions in addition to the above.
Just to add to most of these responses - I would absolutely pause them (don't lose the data!). Then tracking the success, it really depends if you are doing that in the engagement program level or not. You definitely want to have a success associated but you shouldn't double count it (engagement program AND additional sales). Whichever you are using make sure it is synced so the success still shows as responded for SFDC reporting.